Monitoring the Health of Semi-Scavenging Ducks in Bangladesh

Monitoring the Health of semi-scavenging Ducks in Bangladesh Hoque, M.A.1, Brun, E2., Cook, A.J.C.3, Bell, J.G.4, Mostafa, M.G. 4 and Debnath, N.C. 1 1Chittagong Veterinary University, Pahartali, Chittagong-4202, Bangladesh; 2National Veterinary Institute, 0033, Oslo, Norway; 3Veterinary Laboratories Agency, Wybridge, UK; 4 Smallholder Livestock Development Project-2, Farmgate, Bangladesh Abstract A longitudinal study was conducted in Chatkhil Upazila in Bangladesh The objectives were to identify disease problems and generate knowledge to establish a disease surveillance system and recommendations to improve the productivity and health status of ducks. The most important causes of mortality were duck plague and duck plague together with duck cholera. A successful network was established between farmers and the surveillance team through which dead ducks with accompanying information were obtained. Introduction Poultry rearing is an integral part of the rural farming communities in Bangladesh (Amber and Mia, 2002, FAO, 1991). Duck rearing is well suited in the coastal and low-land areas and rural duck rearing, owned and managed by women and children, is important for reducing poverty in resource- poor smallholder families (Pym et al., 2002). Over the past two decades a production system known as the "Bangladesh Poultry Model" has been running in collaboration with private enterprises, governmental and non-governmental organizations. Currently, the Smallholder Livestock Development Project in Five Southern Districts is promoting a simple duck production model, in which some people in rural communities act as duck rearers and others as duck vaccinators (Sarkar et al., 2005). A limiting factor in duck production is infectious diseases. Like many other developing countries, the health information system in Bangladesh especially on duck rearing, is poorly developed. Factors associated with reduced productivity and the risk for economically important diseases remains unidentified. Constraints in optimizing the production system include poor infrastructure, insufficient skilled manpower and resources, and poorly organized systems for collection, collation, management, analysis and dissemination of information. This severely limits the development of effective disease surveillance and intervention policies. Therefore, an epidemiological project was undertaken to identify disease problems and generate knowledge on constraining factors to establish a surveillance system for household ducks and to identify recommendations for interventions to improve production. Materials and Methods A longitudinal study was conducted on 379 household farms selected randomly from 4 different zones of Chatkhil Upazila in Noakhali District, Bangladesh from January 2005 to January 2006. The farms were monitored from 1 month to 13 months. One field investigator was dedicated to each zone. He collected dead birds at farm visits at 3-4 days intervals. Farmers were paid Bangladesh Taka 20 for each dead duck and in some cases, also provided with vitamin supplements for their remaining ducks. During visits, investigators asked for clinical signs related to the dead ducks and for other information including breed, age, sex, and vaccination status against duck plague. Temperature and humidity were recorded from a dry and wet thermometer fixed at the field research centre. Farmers were shown information sheets where different diseases were depicted in order to help standardizing clinical signs. At the field research centre, cloacal swabs were collected and postmortem examinations were performed on the ducks. Tissue samples were immediately frozen in a freezer at -210C before transfer to Chittagong Veterinary University (CVU) at weekly intervals where they were kept frozen at -840C until further analyzed. Impression smears were made from tissues of the liver and heart of the dead ducks immediately after collection for microscopic examination to diagnose duck Proceedings of the 11th International Symposium on Veterinary Epidemiology and Economics, 2006 Available at www.sciquest.org.nz cholera. A total of 325 dead ducks were analyzed. Inoculation of duck embryos and routine bacteriological and microscopy were used for the diagnosis of viral and bacterial diseases. A descriptive statistical analysis was carried out to estimate the frequency of duck diseases Univariate and multivariate Poisson regression were used to assess associations between predictors and the main outcome variable (mortality due to duck plague). A model was established with three predictors (vaccination, sex and environmental humidity) and assessed for overall fit by chi-square goodness-of-fit test. The results were presented as Incidence Rate Ratio (IRR), estimated rate, p- value and 95 per cent confidence interval. Results Table 1 Frequency of the diseases among 325 dead ducks Name of diseases Percentage Duck plague 25.3% Duck plague and Duck cholera 25.3% Duck Cholera 12.4% Duck plague and Duck viral hepatitis 7.7% Negative for above 29.6% Of the total negative samples (29.6%), colibacillosis (33.4%), colibacillosis plus salmonellosis (15.7%) and salmonellosis (7.3%) were diagnosed and 43.8% remained undiagnosed. Increased mortality due to duck plague amongst ducks of unidentified sex (very young ducks) compared to identified sex was RR=3.1 (95%CI-2.3/4.2), non vaccinated compared to vaccinated ducks; RR=1.8; 95% (C.I-1.3/2.4) and >63% humidity compared to £63% humidity; RR=1.6; 95% C.I-1.2/2.1) (p<.05). The estimated mortality rate in ducks of unidentified (very young) and in ducks identified sex ducks was 6.9 and 2.3 deaths per duck-year at risk respectively while the rate in vaccinated and non-vaccinated ducks was estimated as 2.3 and 3.9 respectively. The rates at humidity (£63%) and humidity (³64%) were estimated as 2.3 and 3.5 respectively. During the project period the farmers were motivated to co-operate, and a successful network was established between participating farmers and the surveillance team. Field workers were allowed access to the farms, to interview farmers who kept records of population (introduction of new ducks, mortality and morbidity, clinical signs and symptoms of the sick/dead ducks), therapeutic and preventive information. Discussion Duck plague and duck plague plus duck cholera were registered as the most frequent diseases in this study as previously reported in Bangladesh and other parts of the world (Das et al., 2005; Hoque and Rahman, 2004; Tirath, 2002; Aini, 1993). Salmonellosis and colibacillosis plus salmonellosis have been reported previously in the growing ducks in Bangladesh (Hoque and Rahman, 2004). Some of the bacterial diseases may be transmitted between chickens and ducks because farmers prefer mixed rearing and collibacillosis, salmonellosis and fowl cholera are common endemic diseases for both species. Close contact, droppings, contaminated feed and water may be potential ways of exchanging diseases. As there is not vaccination practiced against duck cholera and duck viral hepatitis, these diseases are likely to occur. Low-grade inter-current diseases together with stress usually results in increased susceptibility to pathogenic organisms (Aini, 1993). Immunisation against duck cholera might have played a vital role in reducing the prevalence of the disease. Adopting sound management, good sanitation, and judicious selection of suitable antibiotics and sulfonamides with timely intervention may control bacterial diseases. Proceedings of the 11th International Symposium on Veterinary Epidemiology and Economics, 2006 Available at www.sciquest.org.nz Growing and non-vaccinated ducks were more affected with duck plague than adult and non- vaccinated ducks (Das et al., 2005; Hoque and Rahman, 2004). So, stress management in the initial weeks (1 or 2) after the start of the growing period supplying saline or glucose water, water soluble vitamins and good housing would give positive results. Ducks should not be allowed to scavenge in contaminated areas and water sources at that stage. Rural poultry flocks make little use of conventional vaccines. However, vaccination against duck plague has been practiced to some extent for ducks in the smallholder livestock development project. Delayed vaccination, vaccination during sub clinical infection state and failure to keep the vaccine refrigerated might have contributed to the duck plague vaccine failure. Since the mortality has occurred at an earlier age in ducks, the vaccination schedule should begin on day 15, boosted at 30 days and subsequent dose after 4 months. Besides this, a field vaccine trial should be carried out to make a proper vaccine schedule for duck plague. The farmer's lack of money and lack of awareness meant that indigenous ducks remained non-vaccinated in the study area and more mortality was recorded in non-vaccinated ducks. As the ducks in unidentified sex were very young and remained unvaccinated, the more mortality was recorded. More mortality was encountered at high humidity because ducks become stressed and susceptible to infectious diseases like duck plague at high humid environment, which might have led to more mortality. Based on the results of this study, small family farms could improve their productivity by applying better management methods and through the use of vaccines or timely application of medications to reduce the impact of disease on their duck population. So far no epidemiological unit has been created within government livestock services. However, authority has been

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