Submitted to: International Journal for Veterinary and Biomedical Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2010
Publication Date: 12/1/2010
Citation: Hailat, N.Q., Hananeh, W.M., Metekia, A.S., Stabel, J.R., Al-Majali, A.M., Lafi, S.L. 2010. Pathology of subclinical paratuberculosis (Johne's Disease) in Awassi sheep with reference to its occurrence in Jordan. International Journal for Veterinary and Biomedical Science. 55(12):590-602. Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle,sheep and wild ruminants, characterized by diarrhea, reduced feed intake, weight loss and death. Animals usually become infected when they are young by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced production by these animals through reduced milk production, they also present a potential infective threat to the rest of the herd. Johne’s disease is difficult to diagnose and therefore to control. An understanding of the extent of infection within sheep flocks in Jordan is key to management and control of the disease. In this paper, we present results from a study designed to investigate the prevalence of infection in Awassi sheep populations in Jordan. Further, two methods of assessment are compared on tissues taken from representative sheep. Results of this study demonstrate that the incidence of disease in Awassi sheep is very high and that the method for determining infection is important to the interpretation of results. This type of study will aid in the evaluation of diagnostic tools for the management of this disease.
Technical Abstract: Paratuberculosis (Johne’s disease) is an incurable infectious, chronically progressive enteric disease affecting domestic and exotic ruminants. The causative agent is Mycobacterium Avium Paratuberculosis (M Johnei). In this study, the occurrence of subclinical Johne’s disease in Awassi sheep is investigated. Histopathological examination of 202 ilea and the corresponding mesenteric lymph nodes was conducted. In addition, immunohistochemical examination, using rabbit polyclonal antiserum, of 134 ilea and 83 mesenteric lymph nodes was also conducted. The prevalence of the disease was 50% and 93% using histopathology and immunohistochemistry techniques, respectively. When the lymph nodes were tested, it was revealed that 79% of them were positive by IHC. The histopathological lesions were graded from '-IV, I being the least severe, based on the type of cellular infiltrate (lymphocytes, macrophages and epithelioid cells) and the severity of the lesions. Grades III and IV were considered positive while I and II were considered suspected. Analysis of the results revealed also that the majority of suspected cases (grades I and II) reacted positive with the IHC. Furthermore, the IHC reactions were classified into three types depending on the number of stained cells and the intensity of the staining (I-mild, II-moderate and III-strong). Direct smears, and tissue sections obtained from the ilea and stained with ZN revealed that out of 219 and 202 samples, 53 (24%) and 22 (11%) were positive respectively. Results of the culture revealed that 22 (10%) out 219 were positive. These results showed that subclinical paratuberculosis in sheep is very prevalent in Jordan and strongly suggest alarming fears of severity of the disease at the national level.