Some risk factors for reproductive failures and contribution of Toxoplasma gondii infection in sheep and goats of Central Ethiopia: A cross-sectional study

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Abstract

Reproductive failure has a negative impact on animal production, health and welfare and ultimately rural economies. In Ethiopia, the factors affecting small ruminant reproductive efficiency are inadequately investigated. A cross-sectional survey was done from November, 2010 to May, 2011 to investigate risk factors of reproductive failures including Toxoplasma gondii infection. Analysis of 1372 sera (787 sheep and 585 goats) from 409 flocks using ELISA showed high flock (59.7%) and animal (31.8%) level T. gondii seroprevalence. An overall 24.9% (341/1372) annual abortion rate (19.6% in sheep and 32.0% in goats) was recorded. Animal level T. gondii seroprevalence was significantly associated with abortion in Ambo and Ada’a-Liben districts (Odds ratio [OR] = 2.31, 95% confidence interval [CI]: 1.42, 3.76; P = 0.001). Questionnaire survey on 199 households of Ambo, Ada’a-Liben and Fentale districts revealed high flock level abortion (57.5%), still birth (28.9%) and neonatal losses (47.9%), which are significantly different between study districts (P < 0.001). Multivariable logistic regression model showed that species (goat), large flock size, pastoral and agro-pastoral production systems, drinking water from river and stagnant water bodies, grazing/browsing in plain land and extensive management were significant predictors of flock level reproductive failures. In the final Zero inflated Poisson regression model number of abortions was significantly higher in goat than in sheep flocks (Incidence risk ratio [IRR] = 1.42, 95% CI: 1.08, 1.87; P = 0.012). It is also significantly higher in pastoral (IRR = 1.81, 95% CI: 1.16, 2.83; P = 0.008) and agro-pastoral production systems (IRR = 1.94, 95% CI: 1.32, 2.86; P = 0.001) than in sedentary production system. Prevention of toxoplasmosis, improved husbandry practices and further epidemiological studies to identify causes of reproductive failures are recommended.

Introduction

Ethiopia possesses about 26.1 million sheep and 21.7 million goats raised in various agro-ecological zones (Central Statistical Authority, 2008) and accounting for about 90% of the live animal/meat and 92% of skin and hides (FAO, 2004) export trade value. In the lowlands, sheep and goats are important means of livelihoods for pastoral communities. Extensive system of management with no or low external input and low output predominates in the country (Gizaw et al., 2010). Despite the huge population, optimal utilization of small ruminants in Ethiopia is constrained by disease, poor feeding, poor management and low genetic endowment (Ademosoum, 1992). Productivity and viability of sheep and goat farms depend largely on reproductive performance which in turn is regulated by genetic and environmental factors (Mellado et al., 2006).

Reproductive failure has a negative impact on livestock production, animal health and welfare and ultimately rural economies. There are several potential underlying causes of reproductive failure broadly categorized into infectious and non-infectious causes (Entrican, 2009). In ruminants, Toxoplasma gondii is among the major infectious causes of abortion which is also zoonotic pathogen (Ortega-Mora et al., 2007, Smith and Sherman, 2009). Non-infectious causes such as chemicals, plants, physical agents are also associated with reproductive failures (Hassig, 2007).

T. gondii infection may cause early embryonic death and resorption, fetal death and mummification (Dubey, 2009, Smith and Sherman, 2009), abortion, still births and neonatal death (Marquardt et al., 2000, Radostits et al., 2007, Dubey, 2009, Smith and Sherman, 2009, Solaiman, 2010). Severity of infection is associated with the stage of pregnancy at which the ewe becomes infected; the earlier the gestation period, the more severe the consequence (Dubey, 2009). These reproductive problems result in the loss of offspring and increased lambing/kidding interval, increased culling, reduced milk production and reduced value of breeding stock, hence leading to major economic losses (Marquardt et al., 2000, Ortega-Mora et al., 2007). Moreover, small ruminant abortion involves considerable public health risk (Ortega-Mora et al., 2007).

In Ethiopia, the factors affecting small ruminant reproductive efficiency and flock productivity are inadequately investigated (Mukasa-Mugerwa and Lahlou-Kassi, 1995) and the association of infectious causes with reproductive failures is largely unknown. However, the few studies undertaken in Ethiopia indicated significant association between Brucella seropositivity and abortion in cattle and goats (Megersa et al., 2011), in goats (Ashagrie et al., 2011) and in sheep (Yosef and Nardos, 2010). Vaccination program for brucellosis does not exist in Ethiopia in any of the animal species. In order to protect and sustain small ruminant industry, boost productivity and design appropriate control programs it is critical to have adequate knowledge about reproductive failures. Therefore, the aims of the present study were to estimate frequency of occurrence of flock level reproductive failures and assess associated potential risk factors including T. gondii infection in three districts of East and West Shoa Zones, Central Ethiopia.

Section snippets

Study areas and population

The study was conducted at Ambo, Ada’a-Liben and Fentale districts of Oromia Regional State, Central Ethiopia. Ambo district (longitude 37° 32′–38° 3′ E and latitude 8° 47′–9° 20′ N) is found in Western Shoa Zone while Ada’a-Liben (longitude 38° 58′ E–39° 22′ E and latitude 08° 22′ N–8° 56′ N) and Fentale (longitude 39.93° E–39° 56′0″ E and 8.975° N–8.58′30″ N latitude) districts are found in East Shoa Zone of Oromia Regional State. The altitude in Ambo and Ada’a-Liben is highland [>2300 m above

Seroprevalence of toxoplasmosis and its association with abortion

An overall 59.7% flock level seroprevalence of toxoplasmosis was found. Flock seroprevalence of toxoplasmosis was significantly different between study districts (P < 0.001) and species of animals (P = 0.001). The highest flock level seroprevalence was recorded from Ada’a-Liben district (80.6%, 95% CI: 71.32, 89.79). Seroprevalence was high in sheep flocks (66.7%, 95% CI: 60.47, 72.86) than goat flocks [Fig. 1].

An overall animal level seroprevalence was 31.8% (95% CI: 29.31, 34.25) and it was

Seroprevalence of toxoplasmosis and its association with abortion

An attempt was made to correlate flock history of reproductive failures (history of abortion, still birth, neonatal losses and number of abortions) with T. gondii seropositivity, since toxoplasmosis is an important cause of abortion in sheep and goats in different countries (Dubey and Beattie, 1988, Radostits et al., 2007, Masala et al., 2007, Smith and Sherman, 2009). According to the present study, significant association between T. gondii seropositivity and animal level abortion was observed

Acknowledgements

The financial support of Oromia regional state Rural Capacity Building, Addis Ababa University, VLIR-UOS Project No. “ZEIN 2010 PR 372” “promotion of the PhD program in veterinary public health at the Faculty of Veterinary Medicine”, Belgium, the Italian National Reference Centre for Toxoplasmosis at the Istituto Zooprofilattico Sperimentale della Sicilia A. Mirri, Italy and partial financial support to Maria Vitale Grant No. RF 2007/RC 2009 from Italian Ministry of Health are highly

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