Nipah virus dynamics in bats and implications for spillover to humans.

Nipah virus (NiV) is an emerging bat-borne zoonotic virus that causes near-annual outbreaks of fatal encephalitis in South Asia-one of the most populous regions on Earth. In Bangladesh, infection occurs when people drink date-palm sap contaminated with bat excreta. Outbreaks are sporadic, and the influence of viral dynamics in bats on their temporal and spatial distribution is poorly understood. We analyzed data on host ecology, molecular epidemiology, serological dynamics, and viral genetics to characterize spatiotemporal patterns of NiV dynamics in its wildlife reservoir, Pteropus medius bats, in Bangladesh. We found that NiV transmission occurred throughout the country and throughout the year. Model results indicated that local transmission dynamics were modulated by density-dependent transmission, acquired immunity that is lost over time, and recrudescence. Increased transmission followed multiyear periods of declining seroprevalence due to bat-population turnover and individual loss of humoral immunity. Individual bats had smaller host ranges than other Pteropus species (spp.), although movement data and the discovery of a Malaysia-clade NiV strain in eastern Bangladesh suggest connectivity with bats east of Bangladesh. These data suggest that discrete multiannual local epizootics in bat populations contribute to the sporadic nature of NiV outbreaks in South Asia. At the same time, the broad spatial and temporal extent of NiV transmission, including the recent outbreak in Kerala, India, highlights the continued risk of spillover to humans wherever they may interact with pteropid bats and the importance of limiting opportunities for spillover throughout Pteropus's range.

Piloting the promotion of bamboo skirt barriers to prevent Nipah virus transmission through date palm sap in Bangladesh.

Drinking raw date palm sap contaminated with infected fruit bat saliva or urine is an important mode of Nipah virus transmission to humans in Bangladesh. Bamboo skirts are an effective way to interrupt bat access to the sap. We conducted a study from November 2008 to March 2009 to explore the effectiveness of higher- and lower-intensity interventions by promoting bamboo skirt preparation and use among sap harvesters (gachhis). We spent 280 person-hours in two villages for the higher-intensity intervention and half that amount of time in two other villages for the lower-intensity intervention. To evaluate the interventions we followed up all gachhis once a month for three months. A high percentage of gachhis (83% in higher-, 65% in lower-intensity interventions) prepared and used a skirt of bamboo or other materials - jute stalk, dhoincha (Sesbania aculeata), or polythene - at least once after intervention. In general, 15% of gachhis consistently used skirts throughout the sap collection season. The intensive nature of this intervention is very expensive for a large-scale programme. Future efforts should focus on developing a low-cost behaviour change intervention and evaluate if it reduces the human exposure to potentially contaminated fresh date palm sap.

Risk practices for animal and human anthrax in Bangladesh: an exploratory study.

INTRODUCTION: From August 2009 to October 2010, International Centre for Diarrheal Disease Research, Bangladesh and the Institute of Epidemiology, Disease Control and Research together investigated 14 outbreaks of anthrax which included 140 animal and 273 human cases in 14 anthrax-affected villages. Our investigation objectives were to explore the context in which these outbreaks occurred, including livestock rearing practices, human handling of sick and dead animals, and the anthrax vaccination program. METHODS: Field anthropologists used qualitative data-collection tools, including 15 hours of unstructured observations, 11 key informant interviews, 32 open-ended interviews, and 6 group discussions in 5 anthrax-affected villages. RESULTS: Each cattle owner in the affected communities raised a median of six ruminants on their household premises. The ruminants were often grazed in pastures and fed supplementary rice straw, green grass, water hyacinth, rice husk, wheat bran, and oil cake; lactating cows were given dicalcium phosphate. Cattle represented a major financial investment. Since Islamic law forbids eating animals that die from natural causes, when anthrax-infected cattle were moribund, farmers often slaughtered them on the household premises while they were still alive so that the meat could be eaten. Farmers ate the meat and sold it to neighbors. Skinners removed and sold the hides from discarded carcasses. Farmers discarded the carcasses and slaughtering waste into ditches, bodies of water, or open fields. Cattle in the affected communities did not receive routine anthrax vaccine due to low production, poor distribution, and limited staffing for vaccination. CONCLUSION: Slaughtering anthrax-infected animals and disposing of butchering waste and carcasses in environments where ruminants live and graze, combined with limited vaccination, provided a context that permitted repeated anthrax outbreaks in animals and humans. Because of strong financial incentives, slaughtering moribund animals and discarding carcasses and waste products will likely continue. Long-term vaccination coverage for at-risk animal populations may reduce anthrax infection.

Piloting the use of indigenous methods to prevent Nipah virus infection by interrupting bats' access to date palm sap in Bangladesh.

People in Bangladesh frequently drink fresh date palm sap. Fruit bats (Pteropus giganteus) also drink raw sap and may contaminate the sap by shedding Nipah virus through saliva and urine. In a previous study we identified two indigenous methods to prevent bats accessing the sap, bamboo skirts and lime (calcium carbonate). We conducted a pilot study to assess the acceptability of these two methods among sap harvesters. We used interactive community meetings and group discussions to encourage all the sap harvesters (n = 12) from a village to use either bamboo skirts or lime smear that some of them (n = 4) prepared and applied. We measured the preparation and application time and calculated the cost of bamboo skirts. We conducted interviews after the use of each method. The sap harvesters found skirts effective in preventing bats from accessing sap. They were sceptical that lime would be effective as the lime was washed away by the sap flow. Preparation of the skirt took ∼105 min. The application of each method took ∼1 min. The cost of the bamboo skirt is minimal because bamboo is widely available and they made the skirts with pieces of used bamboo. The bamboo skirt method appeared practical and affordable to the sap harvesters. Further studies should explore its ability to prevent bats from accessing date palm sap and assess if its use produces more or better quality sap, which would provide further incentives to make it more acceptable for its regular use.

Pig illnesses and epidemics: a qualitative study on perceptions and practices of pig raisers in Bangladesh.

Zoonoses in swine are increasingly becoming a global public health concern. Understanding how livestock farmers perceive animal illnesses will help to develop locally acceptable and effective public health intervention strategies to control and manage zoonoses. The authors describe Bangladeshi pig raisers' perception of pig illnesses and their behaviour towards sick pigs. We collected qualitative data from August 2007 to September 2008. Included in our study are backyard pig raisers from three districts, namely: Faridpur, Chapainobabgonj and Tangail and nomadic herders from six districts, namely: Mymensingh, Tangail, Sherpur, Sirajgonj, Bogra and Pabna. We conducted in-depth interviews (n=34) and made observations of human interactions with pigs (n=18). Pig raisers reported several illnesses that caused their pigs to suffer and die. They had close contact with sick pigs whilst caring for them. They slaughtered sick pigs and consumed and sold the pork if they thought that the pig might die. They believed that pig illness could be transmitted among pigs but not between pigs and humans. The perception of pig raisers on pig illnesses and their behaviour towards sick pigs places them in close contact with potentially infectious pig secretions and excretions. Such exposure could favour zoonotic transmission of infectious diseases. A better surveillance system for pig diseases would provide an opportunity to identify the transmission of diseases, determine whether they pose a risk to humans, or whether they contribute to the emergence of diseases.

Bangladeshi backyard poultry raisers' perceptions and practices related to zoonotic transmission of avian influenza.

INTRODUCTION: Highly pathogenic avian influenza (H5N1) virus (known as "bird flu") is an important public health concern due to its potential to infect humans and cause a human pandemic. Bangladesh is a high-risk country for an influenza pandemic because of its dense human population, widespread backyard poultry raising, and endemic H5N1 infection in poultry. Understanding poultry raisers' perceived risks and identifying their risk exposures can help to develop interventions to reduce the risk of avian influenza transmission. This paper explores the perception of Bangladeshi backyard poultry raisers regarding poultry sickness and zoonotic disease transmission and relevant practices. METHODOLOGY: We conducted a qualitative study using social mapping (n=2), in-depth interviews (n=40), household mapping (n=40) and observation (n=16), in two backyard poultry-raising communities. RESULTS: The poultry raisers recognized various signs of poultry illness but they did not distinguish among diseases using biomedical classifications. They perceived disease transmission from poultry to poultry, but not from poultry to humans. They usually kept sick poultry under the bed. If the poultry did not recover, they were slaughtered and consumed or sold. The poultry raisers had close contact with sick birds while handling and slaughtering poultry. CONCLUSIONS: The poultry raisers are unlikely to follow instructions from health authorities to prevent "bird flu" transmission because many of the instructions ask low-income producers to change their existing practices and require time, money, and financial loss. Villagers are more likely to comply with interventions that help to protect their flocks and address their financial interest.

Use of infrared camera to understand bats' access to date palm sap: implications for preventing Nipah virus transmission.

Pteropus bats are commonly infected with Nipah virus, but show no signs of illness. Human Nipah outbreaks in Bangladesh coincide with the date palm sap harvesting season. In epidemiologic studies, drinking raw date palm sap is a risk factor for human Nipah infection. We conducted a study to evaluate bats' access to date palm sap. We mounted infrared cameras that silently captured images upon detection of motion on date palm trees from 5:00 pm to 6:00 am. Additionally, we placed two locally used preventative techniques, bamboo skirts and lime (CaCO3) smeared on date palm trees to assess their effectiveness in preventing bats access to sap. Out of 20 camera-nights of observations, 14 identified 132 visits of bats around the tree, 91 to the shaved surface of the tree where the sap flow originates, 4 at the stream of sap moving toward the collection pot, and no bats at the tap or on the collection pots; the remaining 6 camera-nights recorded no visits. Of the preventative techniques, the bamboo skirt placed for four camera-nights prevented bats access to sap. This study confirmed that bats commonly visited date palm trees and physically contacted the sap collected for human consumption. This is further evidence that date palm sap is an important link between Nipah virus in bats and Nipah virus in humans. Efforts that prevent bat access to the shaved surface and the sap stream of the tree could reduce Nipah spillovers to the human population.