Tuesday, May 24, 2011

Prejudice or hijacking the science?

I have not worked on V. cholerae nor have I published any peer reviewed article on cholera (even though one of the chapters in my book is focused on cholera). My interest in cholera and V. cholerae started with some questions on viable but non-culturable state of bacteria. Since some of the research methodologies and the conclusions derived from the experimental results were unconvincing (especially, the role of VBNCs in the outbreak of diseases), it prompted me to read more research articles on cholera, which ultimately convinced me that many of the hypotheses on the ecology of V. cholerae are based on assumptions only and are not supported by scientific data. This has led me to the question: are the climate scientists hijacking science or are they simply prejudiced?

The term ‘climate science’, however, needs some clarification. This blog has nothing to do with the global warming and the subsequent weather changes; in fact my knowledge in these subjects is very meager and hence not competent for any comments. I had focused only on the role of climate and environment on cholera outbreak.

The major ‘climate hypotheses’ with regard to V. cholerae and cholera outbreak are
1. aqautic environment is important in the ecology of V. cholerae
2. cholera outbreaks can be correlated to climatic and environmental factors
3. aquatic environment is the major reservoir for V. cholerae and the outbreaks result from the growth of bacteria in these reservoirs
4. V. cholerae was already present in the aquatic environment of Peru and Haiti before cholera outbreak
5. cholera outbreak in Peru and Haiti resulted from the growth of autochthonous V. cholerae
6. ocean currents can carry V. cholerae from the point of origin to distant geographical locations
7. V. cholerae can remain viable for years so as to be carried to distant places through sea
8. resuscitation of VBNCs during favorable climatic conditions is responsible for the cholera outbreak
9. climatic and environmental factors are the major drivers of cholera outbreaks

With the exception of the first and the second, the above hypotheses are scientifically questionable.

It can be noticed that there have been attempts by some of the climate scientists to ignore or underestimate the human factors in order to project or exaggerate the role of climate in cholera outbreak. This is also evident from the recent cholera outbreak in Haiti. When many of the ‘climate hypotheses’ remain unproved even after decades of research, it is tempting to believe that there is much more than simple prejudice.

The blog on cholera and VBNC is ending here. I will continue the blog with persister bacteria and their role in chronic infections next month.

Monday, May 23, 2011

Human-associated factors in cholera outbreak

Until 1970s, it had been believed that the humans were the major reservoirs of V. cholerae and that the organism was incapable of persisting outside the host. However, with the finding that the bacteria can remain as VBNCs in water for long time, the aquatic environment had been widely considered to be the major reservoir of the organism. This shifted the importance from human-to-human transmission to environment–to-human transmission. However, the environmental hypothesis could not explain many aspects of cholera outbreak. Moreover, there are many reports indicating the importance of human factors in cholera outbreak.

1.  Using a model incorporating high asymptomatic ratio and rapidly waning immunity, King et al. (2008) found that the asymptomatic ratio in cholera is very high and that the environmental reservoir is directly responsible for relatively few infections only. Thus, the disease outbreak pattern may depend on the prevalence of human inapparent infections.
2. During the seventh pandemic cholera in Peru, V. cholerae O1 could be isolated from 3% of the total randomly selected, symptom-free individuals with no signs of cholera or diarrhea indicating inapparent infections (Pugliell et al. 1992)
3. As already given in the previous blogs, there are number of reports on the import of the organism from one region to another with the help of human carriers.
4. Cholera outbreak in non-estuarine regions of Zimbabwe, a landlocked country in the middle of Africa, suggest that human-to-human transmission contribute more to the outbreak of cholera than the environment-to-human transmission (Mukandavire et al. 2011)
5. In countries of Africa, the funeral activities (Gunnlaugsson et al. 1998) and the practice of eating together with fingers from the same bowl during funeral feasts (Mukandavire et al. 2011) have been a major cause of cholera spread during an outbreak, indicating the importance of human-associated factors.
6. Epidemiological investigations on cholera outbreak in a psychiatric hospital in Singapore showed that the organism was transmitted through person-to-person contact (Goh et al. 1990).
7. As indicated in the previous blog, cholera outbreak during heavy rainfall and drought may be indicative of human factors rather than environmental factor.
8. Low socioeconomic status, unhygienic practices, lack of latrine facilities, poverty, war and migration, overcrowding etc. (i.e.human factors) are linked to the outbreak of cholera
9. The passage of V. cholerae through human gut would make it ‘hyperinfectious’ that may contribute to the explosive spread of cholera (Merrell et al. 2002; Hartley et al. 2006). Thus, the human host not only allows the growth of the organism but also help in the human-to-human spread. This also underlines the role of hygienic practices in preventing the spread of cholera (Codeco and Coelho 2006).

Thus, the importance of human-to-human transmission can not be overlooked even though the climate theory continues to underestimate or ignore the human factors in cholera outbreak.

Next- Prejudice or hijacking the science?

King et al. 2008. Inapparent infections and cholera dynamics. Nature 454(7206): 877-U29
Puglielli et al. 1992. Symptomless carriage of Vibrio cholerae in Peru. Lancet 339(800): 1056-1057
Mukandavire et al. 2011. Estimating the reproductive numbers for the 2008-2009 cholera outbreaks in Zimbabwe. Proc Natl Acad Sci U S A
Gunnlaugsson et al. 1998. Funerals during the 1994 cholera epidemic in Guinea-Bissau, West Africa: the need for disinfection of bodies of persons dying of cholera. Epidemiol Infect. 120(1):7-15.
Goh et al. 1990. Person-to-person transmission of cholera in a psychiatric hospital. J Infect. 20(3):193-200
Merrell et al. 2002. Host induced epidemic spread of the cholera bacterium. Nature 417(6889):642-5
Hartley et al. 2006. Hyperinfectivity: a critical element in the ability of V. cholerae to cause epidemics? PLoS Med. 3(1):e7
Codeco, C. T. and Coelho, F. C. 2006. Trends in cholera epidemiology. PLoS Med. 3(1):e42.

Friday, May 20, 2011

Human-associated factors vs environmental and climatic factors

Cholera is endemic in South Asian countries especially Bangladesh and India whereas sporadic epidemics occur in South America or parts of Africa. In Bangladesh, the cholera outbreak is usually bimodal with a dominant peak soon after the monsoon and a smaller peak during the spring. In other areas, the outbreak usually occurs once a year, following the monsoon. Cholera outbreak also occurs during the periods of drought. Thus, both the increase and decrease in rainfall can influence the outbreak. Similarly, the water temperature is found to have a correlation with the outbreak. Seasonal peaks are reported in summer months when higher water temperature along with the ‘phytoplankton blooms’ provide favorable conditions for the growth of the organism. Thus, climatic and environmental factors, especially water temperature, salinity, rainfall and the plankton availability are considered as the major drivers that determine the outbreak of cholera. Thus, as per the ‘climate theory’, the aquatic environment is the reservoir for the organism and that the favorable climatic conditions help the growth of autochthonous V. cholerae which may result in the outbreak of cholera. Extreme weather phenomena such as El Nino or La Nina may facilitate the growth of V. cholerae in the aquatic environment, which in turn may trigger cholera outbreak.

Once cholera outbreak occurs, it will be transmitted quickly by secondary transmission mainly through contaminated water used for drinking, cooking or bathing. Contaminated sea foods are another important source of infection.
Even though it is clear that the climatic and environmental factors influence the outbreak of cholera, the important question is whether they are the major drivers of the outbreak. In other words, is it the climate factor that initiates the outbreak or is it only facilitating the outbreak and spread of the disease? Similarly, is the outbreak resulting from the regrowth of autochthonous V. cholerae in the aquatic environment or is it due to the growth of fresh bacteria introduced into the aquatic environment from outside? For example, cholera outbreaks usually occur following the monsoon which led to the suggestion that the amount of rainfall is a direct determinant in the outbreak of cholera. However, in endemic areas such as Bangladesh and India, the unhygienic practice of passing stools in the open space is very common especially among the socially and economically backward group of people. Similarly, the sewage system in such areas is underdeveloped. Hence, heavy rain can result in the washing of stool in open land and in the sewage into rivers and other water bodies, resulting in the contamination of drinking water sources. Thus, the fresh introduction of the organism into water bodies can be responsible for the outbreak and if this is the case, the reservoir would be humans themselves rather than the aquatic environment. Thus, even though rainfall is a ‘climatic factor’ it may have only a facilitating function and the outbreak can be directly related to human factors itself rather than the climatic factors. Similarly, under drought conditions, the availability of potable water may decrease resulting in an increase in the number of people sharing the same water supply thus aggravating unhygienic conditions and providing an environment for cholera outbreak.

A serious disadvantage with the climate theory is that most of the studies that had associated cholera outbreak to environmental/climate factors are based on correlations which had ignored the causal mechanisms behind these correlations (Codeco 2001)

Next- Human-associated factors in cholera outbreak

Codeco, C. T. (2001). Endemic and epidemic dynamics of cholera: the role of the aquatic reservoir. BMC Infectious Diseases 1(1).

Wednesday, May 18, 2011

The fantasy theory on the ecology of V. cholerae

The current scientific theories on the ecology of V. cholerae are more close to a fantasy story. The hypothesis put forward by some scientists are not supported by conclusive data. A hypothetical interview with questions and answers on the ecology of V. cholerae is given below.

Q. How did cholera outbreak start in Haiti or Peru?
Ans: V. cholerae is present naturally in the aquatic environment. We ASSUME that the organism that was already present in Peruvian and Haitian aquatic environment was responsible for the outbreak.

Q. In this case, how did the organism reach Peru or Haiti?
Ans: We ASSUME that the ocean currents might have carried the organism from the point of origin to Peru or Haiti.

Q. It took nearly 30 years for the organism to reach Peru. Can the bacteria remain viable for such a long time if they were carried through the ocean currents?
Ans: Yes. In fact, we have shown that V. cholerae can remain viable in sea water microcosms for up to 2 months. We ASSUME that they can remain viable for many years.

Q. But there were no reports of cholera in these areas for many decades. Moreover, toxigenic V. cholerae had not been isolated before the outbreak. So why scientists missed them if they were already present?
Ans: We ASSUME that the bacteria present there were mainly in the dormant form in a viable but non-culturable state. Because they were in the VBNC state, scientists might have missed them.

Q. So why did the outbreak occur all on a sudden?
Ans: We ASSUME that favorable climatic and environmental factors could have triggered the dormant forms to active and culturable forms. For example, El Nino might have activated the dormant forms in Peru and La Nina might have activated them in Haiti.

Regarding the ecology of V. cholerae, scientists have made lots of assumptions. Even though it is acceptable to make bold assumptions and hypotheses in science, those hypotheses should also be supported by conclusive data. Unfortunately, the ecology of V. cholerae is explained based on assumptions only without much supportive data. If the medical community is not receptive to the climatic causation of cholera, it is mainly due to the lack of conclusive proof.

Next- Human associated factors vs environmental and climatic factors

Tuesday, May 17, 2011

VBNC hypothesis- the foundation on which the 'autochthonous V. cholerae theory' is built

Traditionally, the viability of bacteria is related to its ability to form colonies on agar plates. When they lose the ability to form colonies, bacteria are considered dead. However, in 1982, the laboratory of Dr. Rita Colwell reported that bacteria grown in salt water microcosms for two weeks remained viable even though they lost the ability to form colonies. This state is known as viable but non-culturable (VBNC) state. Later it was reported that a number of bacterial organisms enter VBNC state when grown under different stress conditions like lack of nutrients, low temperature, presence of stressors etc. Even though bacteria under VBNC state lose their ability to form colonies, the removal of stress and/or the addition of nutrients can result in the resuscitation of their culturability. Thus, V. cholerae that enter the VBNC state at low temperatures (below 10°C) can be resuscitated to normal growth by a simple upshift of temperature to 25°C.
In cholera endemic areas like Bangladesh, V. cholerae could be isolated easily from aquatic environment during summer, but not during winter. The difficulty in isolating V. cholerae during winter was explained on the basis of the ability of the organism to enter VBNC state. Thus, during winter, when the temperature is below 10°C, bacteria enter VBNC state and become non-culturable. However, during summer, they resuscitate and regain their culturability. Moreover, during summer they multiply rapidly due to ‘phytoplankton bloom’ which provides nutrients for growth of the organism.
However, the resuscitation of VBNC and its significance has been questioned by many researchers (this aspect has been reviewed in detail in my book). Whereas a number of researchers failed to observe the resuscitation of VBNC both in vitro and in vivo, others could notice resuscitation only in vitro and not in vivo, thus questioning the significance of VBNC in causing an outbreak of a disease. According to many researchers, the growth recovery noticed in a number of experiments was not due to true resuscitation of VBNC but only due to regrowth of a few culturable bacteria. Other researchers consider VBNCs are sublethally injured cells or cells nearing the death that do not have the capability to resuscitate even though they may remain viable for some time. Moreover, in a river microbial community, bacteria may be ingested by predators even before entry to VBNC state, thus reducing the importance of VBNC in natural aquatic systems.
Scientists continue to report the entry of different bacteria to VBNC state without considering the above criticisms (they repeat the same in vitro experiments to prove the resuscitation of VBNCs i.e. incubating a bacterial culture in water or sea water microcosms at low temperature and then ‘resuscitate’ them at high temperatures soon after the entry of organism to VBNC state). Our knowledge on VBNC state has not grown much since it was first reported in 1982. Thus, even after 30 years of research on VBNCs, it has not been conclusively proved that the resuscitation of V. cholerae VBNCs is responsible for seasonal cholera outbreak in endemic areas. How much more time and money need to be invested to prove a hypothesis?

Next- The fantasy theory on the ecology of V. cholerae

Monday, May 16, 2011

Blame it on El Nino or La Nina

Researchers who support the ‘autochthonous V. cholerae theory’ propose that the bacteria present in endemic areas can reach most of the world through ocean currents. As per their theory, the organism are present in the coastal and estuarine environment around the world in dormant forms and are mostly attached to phytoplanktons, zooplanktons, crustaceans and other marine organisms. During favorable climatic conditions, the dormant bacteria multiply enough to constitute an infectious dose for humans resulting in an outbreak. Thus, even though there were no reports of cholera in Latin America before 1991 for nearly a century, it was suggested that the organism was already present in the aquatic environment of Peru before the outbreak. It was argued that, in 1991, due to the effect of El Nino, the surface temperature of the sea increased which helped in ‘phytoplankton blooms’ resulting in the multiplication of dormant bacteria leading to cholera outbreak. Similarly, it was argued that, the effect of La Nina, along with a decrease in water and sanitation quality following an earthquake in Haiti in January 2010, was responsible for the cholera outbreak in October 2010.  Thus, these researchers claim that, it is the climatic and environmental factors that initiate the outbreak of cholera and that the cholera outbreak can be predicted by studying the macro-environmental factors using remote sensing data.

Even though the researchers claim that the bacteria were present in Peru before 1991 or in Haiti before 2010, there have been no reports on the isolation of toxigenic V. cholerae before the outbreaks. But, on the other hand, there are a few reports of isolation of non-toxigenic O1 V. cholerae (Batchelor and Wignall 1988; Levine et al. 1982) and non-O1 V. cholerae (Kay et al. 1984; Finch et al. 1987) from Peru and other regions of Latin America and also from Caribbean (Moore and Mathison 1994) before the outbreak. If non-toxigenic V. cholerae could be isolated before the outbreak, why toxigenic V. cholerae were not reported if they were already present in the environment?

On the other hand, there are a number of research articles that have reported the transport of V. cholerae to distant places with the help of human carriers. Below are a few….
1. Cholera among Belgian travelers who visited Turkey (De Schrijver et al. 2007. Travel Med Infect Dis. 5:236-8)
2. Cholera imported from Senegal to Rimini, Italy (Ciofi degli Atti et al. 2005. Euro Surveill. 10(6):E050630.6.)
3. V. cholerae non-O1, Non-O139 in Slovenia, imported from Tunisia (Strumbelj et al. 2005. Euro Surveill. 10(10):E051020.6)
4. Cholera in a traveler from Haiti to Canada (Bekal et al. 2011. Emerg Infect Dis.)
5. Cholera in U.S. through travelers to Haiti (http://www.medscape.com/viewarticle/734778)
6. Two cases of imported cholera from India in Austrian travelers (Strauss et al. 2004. Euro Surveill. 8(30)
Similarly, it has been reported that the organism can also be imported through food products
1. An outbreak of cholera in Maryland, U. S. associated with imported coconut milk from Thailand (Taylor et al. 1993. J Infect Dis. 167:1330-5)
2. Cholera in Sydney linked to imported whitebait from Indonesia (Forssman et al. 2007. Med J Aust. 187: 345-347)
3. Outbreak of cholera in New Jersey associated with the import of crab from Ecuador (Finelli et al. 1992. J Infect Dis. 166(6):1433-5)

Import of the organism to a developed nation may not result in the outbreak of cholera due to high levels of sanitation conditions and excellent health facilities. On the other hand, when the organism is imported to a region with poor levels of sanitation and hygiene, lack of clean drinking water, poor infrastructure and health facilities, the disease can spread quickly, resulting in an outbreak.

Given the fact that the organism can be carried from one place to another with ease, why El Nino, La Nina or other climatic factors should take the blame for the outbreak of cholera in Peru and Haiti? It is true that, once introduced into a geographical region, the multiplication and the spread of the disease may be facilitated by favorable climatic conditions. However, the theory that climatic factors can initiate cholera outbreaks in non-endemic areas by activating autochthonous V. cholerae remains scientifically questionable.

Next- VBNC hypothesis- the foundation on which the ‘autochthonous V. cholerae theory’ is built

Kay et al. 1984. Vibrio cholerae non-O1 isolated from five people with diarrhoea in Lima. Lancet 1: 218.

Finch et al. 1987. Non-O1 Vibrio cholerae infections in Cancun, Mexico. Am J Trop Med Hyg 36: 393–397.

Levine et al. 1982. The pathogenicity of non-enterotoxigenic Vibrio cholerae serogoroup O1 biotype El Tor isolated from sewage water in Brazil. J Infect Dis 145: 296- -299.

Batchelor RA, Wignall FS, 1988. Nontoxigenic 01 Vibrio cholerae in Peru: a report of two cases associated with diarrhea. Diagn Microbiol Infect Dis 10: 135–138.

Moore, R. and Mathison, GE. 1994. The occurrence of non-O1 V. cholerae in non-potable water samples in Barbados. West Indian Med J. 43: 7-8

Friday, May 13, 2011

More questions on Seas et al. (2000)

I am discussing Seas et al. 2000a in more detail as this is an article that have shown the existence of V. cholerae in Peruvian waters before the outbreak of cholera.
As indicated in the previous blog, the existence of toxigenic V. cholerae in Peru was suggested based on the medical records obtained from nine different hospitals in seven cities along the Northern coast of Peru over the five-month period (September–January) during 1989/1990 and 1990/1991. These hospitals were the largest maintained by the Government of Peru in those cities. Out of more than 3000 patients with diarrhea, seven patients from 1990-1991 period were identified as cholera patients based on the clinical signs (i.e. acute watery diarrhea, severe dehydration with shock, generalized cramps, and signs of severe fluid loss, such as ‘‘washerwoman’s hands,’’ sunken eyes, hoarse voice, poor skin turgor, and oliguria). There were no cases reported from 1989-1990 periods. Authors claimed that these 7 cases were indeed cholera infection and was not caused by other infectious or non-infectious agents.

However, the conclusions of the authors derived from these medical records are questionable because
1. A microbiological confirmation of the above 7 cases is lacking. How can it be assumed that the illness was due to V. cholerae itself based on clinical symptoms alone? In fact, other bacterial species that has the potential to cause acute watery diarrhea are prevalent in Peru (Begue et al. 1994). Out of 143 cases of diarrhea surveyed from December 1992 through May 1993 (i.e. after the cholera outbreak), 31% of the cases were caused by Vibrio cholerae whereas enterotoxigeic E. coli was responsible 22% of the cases and Salmonella, Shigella, Campylobacter, and Aeromonas species were responsible for 10% of the cases (Begue et al. 1994). Similarly, a surveillance of bacterial pathogens associated with acute diarrhea in Lima, Peru between January and April 1995 revealed the role of not only V. cholerae but also other enterobacterial species in causing acute diarrhea (Seas et al. 2000b). Many of the clinical symptoms associated with cholera such as watery diarrhea, dehydration, washerwoman’s hand, sunken eyes, hoarse voice were also observed in those bacterial infections (Seas et al. 2000b). In addition, there are many viral and parasitic infections that can cause acute diarrhea and dehydration. Hence the assumption that V. cholerae was responsible for the above 7 cases based on clinical signs alone is not scientifically acceptable.

2. How did the authors rule out other etiologies in the above 7 cases of illness?  
As per the authors, “All of these other etiologies seem unlikely, however, since no similar cases were identified during the same period in the previous year”. This statement is indeed surprising. Why anyone should expect similar cases in the previous year if it were due to other etiologies?

3. The authors have only reviewed the medical records during two year periods i.e. 1989/1990 and 1990/1991. Based on the records from just two years, authors concluded that the above cases could not be due to other infectious or non-infectious agents. Since medical records of just two years can not reveal much regarding the previous presence or absence of an illness, logic seems to be questionable.

4. Lipp et al. 2002 went further ahead to suggest that multiple strains of V. cholerae could have contributed to the epidemic. What is the basis of such assumption?

To me, this article does not reveal or demonstrate anything regarding the previous presence of V. cholerae in Peru. It is highly unfortunate that, based on clinical signs alone, the presence of cholera in Peru before January 1991 was suggested. Without any supporting data, the authors also suggested that climatic factors might have played a role in the outbreak through the activation of V. cholerae that were already present in Peru.

Next-Blame it on to El Nino or La Nina

Seas et al. 2000a. New insights on the emergence of cholera in Latin America during 1991: The Peruvian experience. Am. J. Trop. Med. Hyg. 62(4): 513-517.
Begue et al. 1994. Diarrheal disease in Peru after the introduction of cholera. Am. J. Trop. Med. Hyg. 51(5): 585-589.
Seas et al. 2000b. Surveillance of bacterial pathogens associated with acute diarrhea in Lima, Peru. Int J Infect Dis. 4(2):96-99.
Lipp et al. 2002. Effects of global climate on infectious disease: the cholera model. Clinical Microbiology Reviews 15(4): 757-770.

Wednesday, May 11, 2011

Was toxigenic V. cholerae present in the aquatic environment of Peru before the outbreak?

Even though cholera outbreak in Peru occurred in January 1991 as per the official records, it was argued that the organism was present in the aquatic environment much earlier. (Read the article “New insights on the emergence of cholera in Latin America during 1991: The Peruvian experience”)

In this article, medical records obtained from different hospitals in Peru over the five-month period (September–January) during 1989/1990 and 1990/1991 were reviewed. It was noticed that seven patients attended emergency rooms for clinical signs of acute watery diarrhea and dehydration between October 1990 and January 1991. i.e. before the official record of cholera outbreak. These patients were residing in different geographical locations separated by about 1000 kilometers. All the patients were given intravenous fluids and none of them died and were discharged after a short period of hospitalization. Based on the clinical signs of these medical records, authors argued that these cases were caused by V. cholerae and that toxigenic V. cholerae was present in the aquatic environment at least 4 months prior to the recognized onset of cholera epidemic. They also argued that since the patients were located in different geographical areas separated by about 1000 kilometers, the epidemic did not start from a single location, but rather from multiple locations.
However, the assumption that cholera started much earlier was solely based on clinical symptoms of patients and those medical records lacked microbiological confirmation of the cause of watery diarrhea as admitted by the authors. Since a number of organisms can cause watery diarrhea (not only bacteria, but also viruses, parasites, food poisoning, chemicals etc.), there is no evidence that the illness was indeed caused by V. cholerae. Moreover, they were isolated cases and there were no reports of the disease spreading to other persons. Similarly, all patients were discharged after a short hospitalization and did not have any complications. On the other hand, once the cholera epidemic began, the disease spread quickly and resulted in a number of deaths.
Thus, based on medical records of clinical cases of watery diarrhea alone, the authors ‘discovered’ that
1. cholera started in Peru at least 4 months before the official recorded cases
2. toxigenic V.cholerae was present in the aquatic environment of Peru before the outbreak
3. cholera outbreak started from multiple locations separated by about 1000 kilometers thus rejecting the single entry hypothesis.

Again, this finding was cited in the subsequent articles and reviews as the evidence for ‘autochthonous V. cholerae theory’.

Can researchers prove the existence of organism in Haiti before October 2010? If they can get the medical records from Haiti which shows at least a clinical case of acute watery diarrhea a few months before October 2010, they can ‘prove’ the autochthonous V. cholerae theory. And, with more than one clinical cases recorded in different geographical areas, they can also reject the single entry hypothesis!!

Next- More questions on Seas et al. (2000)

Tuesday, May 10, 2011

Long distance travel of V.cholerae

Here, I will discuss the article (Munro and Colwell 1996) that had ‘demonstrated’ the long distance carriage of V. cholerae.

The objective of their study was
“The objective of this study was to determine the effect on survival in the marine environment of V. cholerae grown under high osmotic pressure prior to exposure to seawater, in order to test the hypothesis that such survival would allow transport of V. cholerae via ocean currents to distant geographical locations.”

The authors have incubated V. cholerae, pre-grown in different media, in seawater microcosms for 60 days. Bacterial counts were determined during the 60-day period. They found that cells previously grown in 0.5M sucrose showed a decrease of 2 log units after transfer to seawater microcosm for the first 10-12 days and maintained their number for the next 50 days. They also found that cells previously grown in M9 or M9Na showed a decrease of 3-5 log units for the first 10-12 days followed by an increase in the number of cells for the next 50 days to the same number of cells pre-grown in a medium containing sucrose.

Based on the results, the authors concluded that
“In conclusion, this study demonstrates that, under certain conditions, V. cholerae can remain in a culturable state in the marine environment for very long periods of time, months or even years. The significance of this finding is obvious in view of recent outbreaks of cholera in coastal cities of Latin America where transport by oceanic currents is hypothesized.”

Does this finding have any significance as claimed by the authors? The authors were testing the hypothesis that the survival of the organism would allow transport of V. cholerae via ocean currents. Where in this article have they tested this hypothesis? Similarly, where in the article have they demonstrated that the organism can be carried via ocean currents to distant geographic locations? Moreover, isn’t it true that, under certain laboratory conditions, bacteria (not only Vibrio) can remain viable for long periods?

Interestingly, this article has been cited in subsequent reviews as the evidence for the long distant carriage of the organism, thus misleading the readers.

Next- Was toxigenic V. cholerae present in the aquatic environment of Peru before the outbreak?

Munro, P. M. and Colwell, R. R. (1996). Fate of Vibrio cholerae O1 in seawater microcosms. Wat. Res. 30(1): 47-50

Monday, May 9, 2011

‘Ocean current hypothesis’ and Vasco da Gamas of the microbial world

At the end of the 15th century, Vasco da Gama, the Portugese explorer, led an expedition that opened a sea route from Europe to India via the Cape of Good Hope at the southern tip of Africa. Not only humans, but, bacteria such as Vibrio cholerae, the causative organism of cholera, are also good explorers (as per some published research findings)

The seventh pandemic cholera that originated in Indonesia in 1961 reached Peru in 1991 and later spread to many countries of Latin America. Since Latin America was free of cholera for nearly a century, there were many speculations on how the organism might have reached Peru. One of the speculations was that the ocean currents carried toxigenic V. cholerae from endemic areas to Peruvian coasts.

Munro and Colwell (1996), Colwell (1996) and Mourino-Perez (1998) suggest that V. cholerae can remain in seawater for a relatively long time, i.e. sufficiently long to be carried by ocean currents to widely distant geographical locations. So, if the hypothesis is correct and if the source of origin of cholera in Peru is Indonesia or other South-east Asian countries, the organism should have crossed the entire Pacific to reach Peru, after travelling thousands of miles. However, later findings suggested a possible origin in Africa (Lam et al. 2010). Even if this is the case, it can still be argued that there are two routes for the organism to reach Peru via sea. One to cross both the Indian and Pacific Ocean to reach Peru and the second to cross the Atlantic, reach the Southern cone and then move north to reach Peru.

In any case, Vasco da Gama will be envious of the organism!!

Next, I will discuss the article by Munro and Colwell (1996) that have ‘demonstrated’ the long distant carriage of the organism.

Munro, P. M. and Colwell, R. R. (1996). Fate of Vibrio cholerae O1 in seawater microcosms. Wat. Res. 30(1): 47-50
Colwell, R. R. (1996). Global climate and infectious disease: The cholera paradigm. Science 274 (5295): 2025-2031
Mourino-Perez, R. R. (1998). Oceanography and the seventh cholera pandemic. Epidemiology 9(3): 355-357

Friday, May 6, 2011

‘Autochthonous V. cholerae theory’ is wrong in 2010. Was it correct in 1991?

The last paragraph of the chapter ‘Resuscitation of VBNC, outbreak and global spread of cholera’ in my book “The systemic practice of misinterpretation of scientific data” is reproduced below

In short, Dr. Colwell’s group has put forward three theories
1. resuscitation of VBNC is responsible for the seasonal outbreak of cholera in endemic areas
2. the aquatic environment plays an important role in the ecology of V. cholerae, and
3. autochthonous V. cholerae is responsible for the presence of pandemic strains across the world.
            However, out of the three theories, both the first and the third theories remain scientifically questionable.

The book was published on September 2010, one month before the cholera outbreak in Haiti. The hypothesis that autochthonous (indigenous) V. cholerae is responsible for the outbreak of cholera in places distant from their point of origin was not convincing to me on the basis of the cholera outbreak (seventh pandemic) in Peru in 1991.

The seventh pandemic cholera, caused by V. cholerae O1 El Tor, originated in Indonesia in 1961 and later spread to most of Asia and Africa. In 1991, it reached Peru and from there, it spread to many countries of Latin America. Since Latin America was free of cholera for nearly a century, the scientists were unsure of how the organism reached Peru. There were many speculations.
1. Non-toxigenic V. cholerae already present in the aquatic environment of Peru acquired virulence through recombination
2. Toxigenic V. cholerae was already present in coastal waters of Peru
3. Ocean currents carried the organism from endemic areas to Peru
4. The organism was imported to Peru from endemic areas either by travelers or other carriers

Whereas the first two speculations emphasize the importance of autochthonous V. cholerae in the outbreak of cholera, the third one suggests that the organism can be carried to distant places through sea without the involvement of humans. Only the last speculation is based on human-associated factors.
One of the arguments against the proposal that autochthonous toxigenic V. cholerae is responsible for cholera outbreak in Peru is the failure to detect the organism in Latin America before the outbreak. Moreover, there were no reports of cholera in Latin America for nearly a century. Why some cholera researchers are adamant that an outbreak can occur only through the activation of autochthonous V. cholerae? Even if it has to be carried, why it has to occur through sea with the help of ocean currents? If cholera can be carried from Dominican Republic to New York (1), from Thailand to Maryland (2) or from Calcutta to Guinea (West Africa) (3) with the help of humans or other carriers, why it can’t reach Peru from distant locations through carriers? Similarly, why it can’t reach Haiti from Nepal through Nepalese peacekeepers especially since a cholera outbreak had occurred in Nepal just two weeks before they travelled to Haiti?
Autochthonous V. cholerae theory could not be ruled out completely in 1991 because researchers were not able to pinpoint an exact carrier that could have caused the cholera outbreak in Peru. However, with the outbreak of cholera in Haiti in 2010, the above theory may not hold valid. It will be much more difficult for researchers to further support the questionable ‘autochthonous theory’ or ‘ocean current theory’.

Next- ‘Ocean current hypothesis’ and Vasco da Gamas of the microbial world       

3. Sharma et al. 1998. Molecular evidence that a distinct Vibrio cholerae O1 biotype El Tor strain in Calcutta may have spread to the African continent. Journal of Clinical Microbiology, 36 (3): 843-844

Thursday, May 5, 2011

Some interesting quotes on the outbreak of cholera in Haiti

1. On the source of infection

I think it’s very unfortunate to look for a scapegoat. It is an environmental phenomenon that is involved. The reason we don’t know [the catalyst] is because the medical community is not receptive to climactic causation or correlation.”-Dr. Rita Colwell, University of Maryland

“A single source — such as the UN peacekeepers camp — would not have caused such a massive and rapid spread of cholera” - Dr. Rita Colwell (http://humanosphere.kplu.org/2010/11/experts-say-un-did-not-bring-cholera-to-haiti-it-was-already-there)

“Cholera was originally in the Artibonite River”- Emmanuelle Schneider of the United Nations Office for the Coordination of Humanitarian Affairs

"Vibrio cholerae, the bacterium responsible for cholera, may have been dormant in water until weather-related conditions caused it to multiply enough to constitute an infective dose if ingested by humans,"- Dr. David Sack, Johns Hopkins University Bloomberg School of Public Health

However, not everyone is convinced….

the idea that a microbe so closely resembling a South Asian strain would emerge in Haitian waters is “frankly absurd” - Dr. Matthew Waldor of Harvard Medical School

"Human activity coming from a far-away place brought this strain to Haiti"-Dr. John Mekalanos, Harvard Medical school

"It started in the centre of the country, not by the sea, nor in the refugee camps. The epidemic can't be of local origin. That's to say, it was imported,"- Dr.Renaud Piarroux, French epidemiologist

2. On whether the peacekeepers were tested for any infections

“There is no contamination on the base. We have conducted several tests, and all of them have come negative” -Vincenzo Pugliese, deputy spokesman of the the U.N. Stabilisation Mission in Haiti on the report that cholera outbreak in Haiti was caused by river contamination by Nepalese troops

"We strongly condemn the making of such allegations with no firm evidence or facts"- Ramindra Chhetri, Nepal Army Brigadier General and the army spokesman on the report that cholera outbreak in Haiti was caused by river contamination by Nepalese troops

“Before they selected for peacekeeping deployment, the peacekeepers have to go through strong health vetting. There is no possibility of any infection in the new batch of soldiers as they have to undergo a ‘through medical checkup’ before participating in the peace keeping mission,”- Ramindra Chhetri, Nepal Army Brigadier General

Different voices were also heard….

None of Nepal's soldiers serving with UN peacekeepers in Haiti was tested for cholera before they went- Brig Gen Dr Kishore Rana, the Nepalese army's chief medical officer (http://www.bbc.co.uk/news/world-south-asia-11949181)

3. On whether it is important to know the source of infection

“The question of how it came here is not central in Haiti. What's central is making sure people do not die and know how not to get sick.” – Dr. Robert Tauxe, deputy director of the Division of Foodborne, Waterborne and Environmental Diseases for the CDC

“If an epidemic killed 4000 people in Europe or the U.S., we would want to know exactly where it came from. So why not when the same happens in Haiti?”-Dr.Renaud Piarroux      

Next- ‘Autochthonous V. cholerae theory’ is wrong in 2010. Was it correct in 1991?

Wednesday, May 4, 2011

Are researchers responsible for cholera deaths in Haiti?

Cholera outbreak that began in Haiti in October 2010 had affected more than 200,000 people and resulted in more than 4000 deaths. Since then, cholera has been reported in neighboring Dominican Republic and also in U.S. and Canada.

Since Haiti was free of cholera for nearly 50 years, the immediate question was how the disease suddenly appeared in Haiti (although cholera outbreak occurred in Latin America in 1991, it did not reach Haiti at that time). A mission report by Renaud Piarroux, a French epidemiologist and a renowned cholera expert, had no doubt that the organism was imported from South Asia, most probably by U.N. peacekeepers from Nepal. The unpublished mission report by Renaud Piarroux can be read at http://www.ph.ucla.edu/epi/snow/cholera_haiti_piarrouxreport.html

The reasons why the cholera outbreak in Haiti is proposed to be a case of imported one are
-Nepal and other South Asian countries are endemic to cholera and cholera outbreak had occurred in the capital city of Kathmandu, Nepal on September 2010
-UN peacekeepers from Nepal arrived in Haiti between October 8 and 15, 2010
-The first confirmed case of cholera showing the symptoms was reported on October 14, 2010
- As per Dr. Ralph Frerichs, “taking into account an incubation period of 2-3 days, the two events (i.e., arrival of troops and onset time of initial case) were closely related in both place and time”.
- The first patients in Haiti used to drink water from a tributary of the Artibonite River flowing just below the base of United Nations Stabilization Mission, where the peacekeepers were staying
- People reported that a nauseating liquid poured from pipes from the base at the time the outbreak occurred
- The Haitian V. cholerae isolate was found to be closely related to the variant strain predominant in South Asia and was distinct from those circulating in Latin America and U.S. Gulf coast (Chin et al. 2011).

Nepal Government and the U.N. were quick to reject the findings in the report. So were some cholera researchers like Dr. Rita Colwell, University of Maryland. According to Dr. Colwell, the organism was present in the aquatic environment of Haiti already and the outbreak could be related to climate patterns especially to La Nina. She commented “I think it’s very unfortunate to look for a scapegoat. It is an environmental phenomenon that is involved. The reason we don’t know [the catalyst] is because the medical community is not receptive to climactic causation or correlation.”( http://www.circleofblue.org/waternews/2010/world/hold-cholera-in-haiti-the-climate-connection). However, as per Dr. Matthew Waldor of Harvard Medical School, “the idea that a microbe so closely resembling a South Asian strain would emerge in Haitian waters is “frankly absurd”

For scientists who had spent 3-4 decades in cholera research and who had received millions of dollars of grants towards their research on the environmental and climactic patterns in cholera outbreak, the embarrassment is understandable and evident. Now the medical community is blamed for not being receptive to the climactic causation. However, if the medical community can not be convinced even after 3-4 decades of research, after utilizing millions of dollars, the problem lies elsewhere.
From 1980s onwards, the focus of cholera research almost completely shifted to environmental and climactic factors and ignored human-associated factors even though there were sufficient evidences for the latter. Had the researchers given the deserved importance to human factors, they could have warned the scientific community and U.N. effectively about the possible cholera outbreak in Haiti and thus could have averted thousands of deaths. Misinterpretation of scientific data, thus, results not only in the wastage of money, but can also cost lives. This is another lesson Haiti has taught us, but only time will tell whether we had learned anything.

Next- Some interesting quotes on the outbreak of cholera in Haiti

Chin et al. (2011). The origin of the Haitian cholera outbreak strain. N Engl J Med. 364(1):33-42.

Tuesday, May 3, 2011

My first post to this blog…..

After the publication of my book on September 2010, two events caught my attention. One was the cholera outbreak in Haiti in October 2010 and the other was NASA’s announcement in December 2010 on the discovery of an ‘alien form’ of bacteria that had come under fire from a number of researchers worldwide. While the former was strong evidence against the current knowledge on the ecology of Vibrio cholerae (dealt in detail in my book), the latter revealed the pitfalls in the current peer-reviewed system.

In the book, I had provided some examples of questionable research findings that are published in peer-reviewed journals. Some of these occur from human errors; however, one can also see intentional attempts of some researchers to promote their preconceived hypothesis. I had argued that it is possible to identify the flaws in scientific research by scrutinizing the subject matter thoroughly, which can save both time and money.

National Institute of Health (NIH) spends nearly 30 billion dollars an year for medical research. As per NIH website, 80% of the money is awarded through nearly 50,000 grants to more than 325,000 researchers. In spite of the huge amount of money invested in medical research, competition for grants has increased considerably in the recent years. With the current economic recession and the public outcry to reduce governmental spending, the situation may only become worse. Researchers will feel relieved if the current spending on science is at least maintained.

Under the current circumstances, is it worth to support all the current projects? By scrutinizing each research project thoroughly, is it possible to save money and improve the quality of science?

I will start with the recent cholera outbreak in Haiti and the lessons science can learn from it.

Next- Are researchers responsible for cholera deaths in Haiti?