Sheep and goats farming is particularly important commercially, culturally, and socially in the central Zagros region. This cold region is notable for its altitude of more than 2000 meters above sea level. Our observations led to the isolation of 8 and 6 Eimeria species from sheep and goats, respectively, with E. granulosa and E. faurei in sheep and E. jolchijevi and E. caprina in goats being the most prevalent. This subject is contradicting to previous studies. Catchpole et al (1976) isolated 11 Eimeria species from sheep (Catchpole et al. 1976), that E. ovinoidalis being the most virulent, while Kaufman (1996) declared E. arloingi, E. christenseni, and E. ninakohlykimovae to be extremely pathogenic for goats (Kaufmann 1996). These data show that geographical district has an effect on the virulence of Eimeria species and this is the first report of E. granulosa as the most pathogenic species for Lori-Bakhtiari sheep in Iran. Yakhchali and Zareei (2008) and Yakhchali and Rezaei (2010) were reported that the most common sheep Eimeriosis in Malayer and Tabriz suburbs are belonging to E. intricata (Yakhchali and Zareei 2008; Yakhchali and Rezaei 2010). Researches on goats Eimeriosis in other districts of Iran indicate that E. arloingi is more pathogenic (Hashemnia et al. 2015; Kheirandish et al. 2014; Razavi and Hassanvand 2006), while in the central Zagros region, the predominant species is E. jolchijevi followed by E. caprina. It can be assumed that over the centuries, immunity to some species has occurred in the central Zagros region.
The annual prevalence of clinical coccidiosis was estimated to be 13.66 percent which lambs and kids under the age of 6 months excreting more oocysts than the other age groups. High oocyst excretion rate and severe pathogenicity of Eimeria in lambs and kids have already been confirmed by many researchers (El-Alfy et al. 2020; Hashemnia et al. 2015; Keeton and Navarre 2018; Razavi and Hassanvand 2006; Yakhchali and Zareei 2008; Yakhchali and Rezaei 2010). Constable et al (2016) explained that artificial infection with E. ninakohlyakimovae was very harmful to lambs, however natural infection with numerous species of Eimeria had no effect on their growth rate (Constable et al. 2016). It has also been demonstrated that young animals who have never been exposed to coccidia are more sensitive to infection and have a high case-fatality rate. On the other hand, excessive stress in elderly animals can result to immunosuppression, which can lead to clinical coccidiosis and oocyst shedding (Pugh and Baird 2012). Because coccidia immunity is specific but not solid, large quantities of oocysts may cause continuous reinfection and raise the level of environmental contamination. Furthermore, pathogenic and non-pathogenic Eimeria species can infect livestock at the same time (Keeton and Navarre 2018). As a result, in addition to oocyst excretion, clinical signs of coccidiosis should be addressed. Our findings revealed that 51.82 percent of positive cases (85 cases) had particular clinical signs, whereas others just excreted the oocysts.
Many studies believe coccidiosis is host specific (Constable et al. 2016; Keeton and Navarre 2018; Pugh and Baird 2012), and our findings rule out the potential of transitory co-infestation between sheep and goats using molecular assay as well.
The incidence of coccidiosis was higher in yearling sheep and those under 6 months of age than in adults, which was consistent with other findings (Kheirandish et al. 2014; Kyriánová et al. 2017; Yakhchali and Zareei 2008; Yakhchali and Rezaei 2010; Yan et al. 2021) but contradicted Al-Saadoon and Al-Rubai (2018) conclusion (Al-Saadoon 2018). Silva et al (2012) have believed that acquired immunity is the main reason for decreasing oocytes excretion in adult sheep (Silva et al. 2011), however, rams may shed more oocysts during the breeding season in response to high testosterone levels.
This study showed that oocyst excretion was considerably higher in the spring and summer than in the autumn and winter, which is similar to Yan et al 's findings for the spring. In contrast, Constable et al (2016), Yakhchali and Rezaei (2010), and Yakhchali and Zareei (2008) believe that oocyst excretion is higher in late autumn and throughout the winter. Yan et al. (2021) also stated that the intensity of coccidia infection was lower in semi-arid, semi-humid, and cold areas with long winters and short summers than in similar areas with higher annual average temperatures and lower average precipitation (Yan et al. 2021). The central Zagros region is a mountainous, semi-humid and cold region with average rainfall which its southern counties are warmer than others. But the height of the western (2365 meters), eastern (2432 meters) and central (2310 meters) counties are more than northern (1963 meters) and southern (1556 meters). In this study, the rate of oocyst excretion in sheep was higher in the central and western counties than in the southern ones. In goats, however, annual oocyst excretion was higher in eastern counties than in the south and west. These findings imply that altitude plays a role in enhancing sheep oocyst shedding.
It is concluded that several environmental conditions, such as high altitude, play an important role in sheep oocyte excretion in the central Zagros region. Coccidia prevalence was also shown to be higher in the spring, among females, and among the younger generation.