Are poultry or wild birds the main reservoirs for avian influenza in Bangladesh?

Avian influenza viruses (AIV) are of great socioeconomic and health concern, notably in Southeast Asia where highly pathogenic strains, such as highly pathogenic avian influenza (HPAI) H5N1 and other H5 and H7 AIVs, continue to occur. Wild bird migrants are often implicated in the maintenance and spread of AIV. However, little systematic surveillance of wild birds has been conducted in Southeast Asia to evaluate whether the prevalence of AIV in wild birds is higher than in other parts of the world where HPAI outbreaks occur less frequently. Across Bangladesh, we randomly sampled a total of 3585 wild and domestic birds to assess the prevalence of AIV and antibodies against AIV and compared these with prevalence levels found in other endemic and non-endemic countries. Our study showed that both resident and migratory wild birds in Bangladesh do not have a particularly elevated AIV prevalence and AIV sero-prevalence compared to wild birds from regions in the world where H5N1 is not endemic and fewer AIV outbreaks in poultry occur. Like elsewhere, notably wild birds of the orders Anseriformes were identified as the main wild bird reservoir, although we found exceptionally high sero-prevalence in one representative of the order Passeriformes, the house crow (Corvus splendens), importantly living on offal from live bird markets. This finding, together with high sero- and viral prevalence levels of AIV in domestic birds, suggests that wild birds are not at the base of the perpetuation of AIV problems in the local poultry sector, but may easily become victim to AIV spill back from poultry into some species of wild birds, potentially assisting in further spread of the virus

Studies on Defective Interfering Particles of West Nile Virus.

The studies undertaken in this thesis described the biological characteristics of defective interfering (DI) particles of West Nile (WN) virus both in vitro and in vivo. A reliable and reproducible assay was developed to measure the interfering activity of DI virus (the optimum interference assay [OIA]) based on ability of DI WN virus to cause a reduction in the yield of infectious standard (STD) WN virus. The sensitivity of the assay was found to be dependent on several parameters of which the cell type used in the assay was the most crucial. High-multiplicity serial passages of STD WN virus in Vero and LLC-MK2 cells generated and amplified a large quantity of DI WN virus as measured by the OIA and their presence was detected as early as after two serial passages. Propagation of pre-formed DI virus in seven cell lines demonstrated that SW13 cells would propagate STD WN virus only and no detectable DI virus was propagated in this cell line. Intraperitoneal inoculation of adult mice with DI WN virus protected them from a lethal challenge by the neurotropic STD WN virus inoculated by the same route. The multiplication of infectious virus in the brains of mice treated with live DI virus was greatly reduced compared to mice inoculated with STD virus and infectivity was rapidly eliminated. Evidence was produced to show that DI virus was propagated in the brain of mice protected by live DI virus. A minority of protected mice sampled at 19 days post infection had infectious virus in their brains suggesting that DI virus can modulate the acute WN virus infection and cause it to become persistent. Virus isolates collected from the protected mice demonstrated three categories of virulence for adult mice: as virulent as the parent virus, intermediate virulence and greatly attenuated. DI virus derived from three different strains of WN virus demonstrated heterotypic interference both in vitro and in vivo. Interference was limited between different members of the WN subgroup of the Flaviviridae and the extent of heterotypic interference was found to be consistent with the antigenic classification of flaviviruses. Thus, interference by flavivirus DI particles may be useful in the classification of flaviviruses. In conclusion, DI WN virus was generated with properties similar to those of DI virus reported for other RNA virus systems. However, the ability of the DI WN virus to protect mice was superior to that of any other virus systems described to date. Thus, DI WN virus may be an excellent system with which to study the biological properties of DI virus

A survey of gastro-intestinal parasitic infection in domestic and wild birds in Chittagong and Greater Sylhet, Bangladesh

A survey of gastrointestinal parasitic infection as determined by faecal examination was conducted among domestic and wild birds in Bangladesh. Birds were sampled from households, wet markets and wetlands in Chittagong and Greater Sylhet districts during April 2012 to February 2013. Mist nets were used to catch resident wild and migratory birds. The overall prevalence of parasitic infection ranged among locations from 25 to 55% in indigenous domestic ducks (live bird samples = 304), 20% in resident wild birds (environmental faecal samples = 40) and 40% in migratory birds (live bird samples = 35). The prevalence of parasitic infection was significantly higher in indigenous domestic ducks collected during summer (39%) than winter (22%) (p = 0.04). In domestic indigenous ducks and Muscovy ducks, both single and multiple types of parasitic infections were found. However, other domestic birds and wild birds often had a single type of parasitic infection. Ascaridia spp. with an average egg load of 50–900, was commonly detected in faecal samples of domestic and wild birds in this study. Other identified parasites were Capillaria spp. and Heterakis spp. both in domestic and wild birds. Improvement of biosecurity measures for household duck farms through educating and motivating household farmers could help mitigate the effects of parasitic infection on production