Small Ruminant Reproductive Health Problems: Risk Factors and Public Health Risk of Infectious Causes of Abortion in Ethiopia

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Reproductive performance is a key determinant for the efficiency of small ruminant production. However, low productivity per animal and flock limits the potential contribution of sheep and goats for rural households in Ethiopia. The overall objective of this Ph.D. thesis is to generate information on the cause, magnitude, and risk factor of reproductive health problems, and public health risk of infectious causes of small ruminant abortion. A cross-sectional study design was used to collect data in three production systems of Ethiopia between July 2018 to February 2019. Two districts from lowland mixed crop-livestock production system, two districts from lowland pastoral production system, and one district from highland mixed crop-livestock production system were selected from Amhara, Oromia, and Southern Nation, Nationality and People (SNNP). Abergelle and Zequala districts in the Wagihimira zone of the northern part of the Amhara region were selected to represent the lowland mixed crop-livestock production system. Yabello and Elwaya districts in the Borena zone from the southern part of the Oromia region were selected to represent the lowland pastoral production system. Doyogana district in Kembata Tembaro Zone from the SNNP region represented a highland mixed crop-livestock production system. The structured questionnaire and laboratory analyses of serum samples were used to generate information for this Ph.D. thesis. Information was collected form the total of 327 households where data on pregnancy outcomes and management risk factors were collected for 299 goat and 242 sheep flocks, serum samples were collected from a total of 1,402 animal (980 goats and 422 sheep). To develop a novel quantitative tool to determine goat annual reproductive performance index at flock level (Chapter 3), the reproductive performance of the flock was estimated based on the annual reproductive output, kidding interval and annual reproductive wastage, principal component analysis was used both as reproductive measures dimensional reduction technique and to develop the final model to predict reproductive performance scale. Then the final algorithm is developed to estimate the goat annual reproductive performance index. To estimate the magnitude of abortion and associated factors (Chapter 4), a causal diagram was generated to identify causal relationships between the potential predictors and Zero-inflated negative binomial regression model was used to determine the associations. To determine the seroprevalence abortion causing pathogens (C. burnetii, C. abortus, Brucella spp., and T. gondi ) and associated risk in sheep and XI goat in three production systems of Ethiopia (Chapter 5), a multilevel mixed-effects logistic regression model was fitted to account for the clustering of animal within villages and households. The 2-PL Item Response Theory (IRT) model was fitted to determine the probability of a person appropriately respond to an item with a provided zoonotic disease KAP level.Based on developed algorithm to measure goat annual reproductive performance, the flocks were classified into good, moderately and poor performing. Good performing flocks has higher scores for reproductive output measures, lower scores for reproductive wastage and lower kidding interval. Many of the flocks were moderately affected by reproductive failures, consequently categorized as moderately performing flocks. Results showed that 142 (58.68%) goats and 53 (17.73%) sheep flocks reported abortions in the 12 months before the survey. The mean annual flock abortion percentages were 16.1% (±26.23) for does and 12.6% (±23.5) for ewes. The final zero-inflated negative binomial regression analysis result indicated that spending the night in traditional sheep house’, ‘providing supplementary feed for pregnant dams’, ‘presence of other livestock species and dog in the household’ had a marked effect on the rate of abortion in sheep and goat flocks. In addition, exposure of the flock to Brucella spp. or anyone of four tested infectious agents significantly increased the risk of abortion in the flock. Overall, 65.41% of sheep and 92.22% goat flocks tested positive for one or more abortion-causing agents, namely, C. burnetti, C. abortus, Brucella spp., and T. gondii; mixed infection was found in 31.58% sheep and 63.33% goat flocks (Paper III). From the total tested animal, 231(16.48 %), 95 (6.78%), 124 (8.84%), and 137(11.42%) were found seropositive for C. burnetii, Brucellas spp., C. abortus, and T. gondii, respectively. Co-infections of abortion pathogens were observed where C. abortus (86.84%) showed the highest level followed by Brucella spp. (78.34 %) and C. burnetii (72.72%) (Paper IV). In the final chapter of this Ph.D. research (Paper V) The attitude subscale had the highest total mean score (37.3, ± 28.92 %) and the knowledge subscale had the lowest mean score (22.4, ± 33.6 %) among the three subscales. Pieces of work in this Ph.D. thesis highlighted the multifactorial nature of small ruminant abortion where animal management, agroecological and infectious disease factors play an important role in its occurrence. There is a need for an integrated approach that improves the nutritional state of pregnant dams through targeted supplementary feeding, abortion management through appropriate biosecurity practices, and vaccination programs for major infectious causes of abortion and herd health management through better veterinary services. Serological study of the four infectious abortion-causing agents demonstrated that all the four infectious causes of abortion XII are widely distributed across three agro-ecologies and production systems might play an important role in sheep and goat abortion and impact the health of the public. Future studies which aim at identifying and characterization several possible abortion pathogens and their public health and socioeconomic impact should be done. The part of this Ph.D. thesis revealed overall low zoonotic disease knowledge, low attitude towards zoonotic disease risk, and common risk behaviors among smallholder farmers and pastoralists. There is a need to continue public education programs to raise the awareness of the communities towards the proper installation of personal protection measures and appropriate disposal of abortion materials to reduce the public health risk from zoonotic diseases.


PhD Thesis


Abortion, Co-infection, Multi-pathogens, Risk factors