Chicken Health Management Practices and Epidemiology of Key Poultry Respiratory Pathogens in Central Ethiopia

Abstract

<p>The commercial poultry industry is not well developed in Ethiopia. On the other hand, compared to many countries in Sub-Saharan Africa (e.g. Kenya, Rwanda etc.) the small-scale chicken egg production value chain is relatively well developed. With decreasing grazing land availability and increasing population size, poultry production is considered as the principal means of providing the poor with good quality animal protein, energy and minerals. Chickens are predominantly kept in village based free-range, scavenging systems with small-scale intensive chicken production contributing less than 10% of chicken products in the country. This free range, scavenging production system is not well developed since it is constrained by many factors.</p> <p>Among the factors that hinder the poultry industry in Ethiopia, disease is ranked the first most important production constraint in the scavenging production system and the second in the commercial production system. The country is reported to lose half of its chicken population every year due to disease. The poor implementation of chicken health management practices in scavenging or small scale intensive production systems predisposes them to disease.</p> <p>Often an acute highly fatal disease of poultry which locally known as “fengil” is blamed for chicken disease outbreaks occurring in the country. Some experts believe the “fengil” syndrome is due mostly to Newcastle Disease (ND) and blame it for most respiratory cases happening in the field. But, since multiple aetiology and complexity are characteristic features of respiratory disease of poultry, it is important to identify non-Newcastle Disease pathogens circulating in the field. There are serological and molecular reports on some important respiratory pathogens of chickens circulating in the country. To address current gaps in knowledge this thesis also has the following objectives: 1) to compare chicken health management practices and perceptions in smallholder commercial and scavenging chicken enterprises in central Ethiopia; 2) to determine the presence, and prevalence of infection with selected respiratory pathogens of chickens in central Ethiopia by serological testing; 3) to determine key risk factors for the serological presence of these pathogens in this region; and 4) to investigate the involvement of respiratory pathogens in clinical disease in the central live chicken markets of Addis Ababa and undertake comparative molecular characterisation of the detected pathogens.</p> <p>To achieve the first objective a cross-sectional survey of chicken health management practices was conducted on small-scale intensive (SSI) and scavenging chicken (SCAV) enterprises in central Ethiopia. The results of this study are reported in Chapter 3. In order to achieve the second and third objectives a cross-sectional serological survey and assessment of the risk factors for seropositivity were conducted in SCAV and SSI chicken holdings in the East, West and North Shewa Zones of central Ethiopia. The fourth objectives was achieved by investigating the presence of different pathogens in the clinical respiratory cases in the central live chicken markets of Addis Ababa (Chapter 6). </p> <p>Under objective 1 an important finding was that seropositivity for the pathogens was more frequent in the SCAV system than SSI system. There was also better vaccination coverage and biosecurity measures implementation in the SSI than SCAV production system. “Fengil” was the main disease condition reported by farmers in the SSI system, with non-specific digestive symptoms being most widely reported in the SCAV system. Farmers in the SCAV system farmers relied widely on use of traditional medicines whereas those in the SSI system used more modern medicines. This suggests that disease prevention and health management are improved with intensification. It was also observed that there is considerable potential to improve practices in both systems. Under objective 2 serological evidence of a high level of exposure to all five selected pathogens (avian meta-pneumo virus (aMPV), Infectious laryngotrachities (ILTV), Infectious bronchitis virus (IBV), NDV and Mycoplasma gallisepticum (Mg)) was detected, including the first report on the seroprevalence of aMPV, ILTV and IBV on the farms located in East Shewa Zone. These pathogens could potentially contribute to or complicate the fengil syndrome, which is commonly ascribed to NDV. </p> <p>Exposure to multiple pathogens was common in more than half of the chickens tested. But, the role of these pathogens in the causation of respiratory disease in the field requires further investigation. Under objective 3 there were 17 risk factors found to have a significant effect on the prevalence of at least one pathogen during the univariate analysis. However only nine of these 17 risk factors were found to influence sero-positivity for one or more pathogens following multivariate analysis. Of the nine risk factors, eight of them influenced more than one disease. The most important risk factor was farmers’ duration of experience in chicken production with shorter periods associated with reduced seropositivity. Other important risk factors were increased contact with wild birds and other animals, season and location. </p> <p>Therefore improved biosecurity measures aimed at minimising contact is recommended to reduce exposure to these diseases, but proper implementation is only possible in the SSI </p> <p>system. Reduced disease prevalence in holdings with less experience may be indicative of owner complacency and pathogen build up in older holdings that could be addressed with targeted extension programs. The provision of dedicated housing for chickens at night should be encouraged in the SCAV system and the disease control programs could be effectively concentrated in the North Shewa zone. The pathogens associated with clinical respiratory disease are not well defined in the country. The objective 4 study of chickens with respiratory disease from the central live chicken markets in Addis Ababa revealed that all the chickens were PCR-positive for aMPV, and most of the sick chickens (17/18) were PCR positive for more than 3 pathogens. Potentially pathogenic bacteria such as <i>Escherichia coli, Klebsiella<i> spp., <i>Streptococcus<i> spp. and <i>Staphylococcus<i> were also isolated. This shows a high level of exposure to multiple respiratory pathogens. Disease was a major constraint in both SCAV and SSI production systems. The acute respiratory diseases which locally known as “fengil” is blamed for most disease outbreaks. Poor uptake and implementation of management practices likely contribute to the high incidence of disease. The poor chicken health management practices identified in both the SCAV and SSI production system likely contribute to the high sero-positivity of chickens for aMPV, ILTV, IBV, Mg and NDV. IN flocks not vaccinated against NDV sero-positivity of chickens for aMPV, ILTV, IBV, Mg was higher than for NDV indicating that non-NDV respiratory pathogens are circulating in the study area to a greater extent than NDV. The investigation of clinical respiratory disease in the central live chicken markets of Addis Ababa directly confirmed the presence of these pathogens in clinical cases with multiple pathogens commonly detected from individual chickens. These shows that outbreaks of clinical respiratory disease of chickens in the country may involve pathogens other than NDV and may well involve infections with multiple agents. Based on the finding of lower disease seroprevalence and higher uptake of recommended disease control practices on SSI farms it is recommended that the program of intensification of smallholder chicken production be continued. Further studies more clearly linking respiratory pathogens with clinical disease need to be carried out, and based on the findings of these, vaccines for significant respiratory pathogens should be developed or imported. </p>