Razieh Heidari - Department of Quality Control, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization, (AREEO), Karaj, Iran.
Vahid Noaman - Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization, (AREEO), Karaj, Iran.
Hedieh Jafari - Razi Vaccine and Serum Research Institute, Agricultural Research Education and Extension Organization, Ahvaz, Iran.

Background: Anaplasma sp. is a blood protozoon that causes economic damage to the livestock industry. Therefore, studying this disease’s epidemiology and distribution pattern in different regions is essential. Objectives: This study aimed to investigate the variety of infections of the Anaplasma sp. in the sheep population of Khuzestan Province in Iran.Methods: A total of ۲۰۰ sheep blood samples were randomly collected and examined using specific nested polymerase chain reaction (nPCR) based on the ۱۶S rRNA gene. Results: The prevalence of Anaplasma phagocytophilum was ۱۷%, and infected sheep had no clinical signs. The effective risk factors in the spread of infection in Khuzestan Province include sheep aged ۳-۵ years, low sanitation, high-density farms, use of acaricides in the field, and hot season (P≤۰.۰۵). There was no significant association between the occurrence of A. phagocytophilum infection and variables of altitude, farm type, vectors, distance from other farms, and sex.Conclusion: Since the infection often has no clinical symptoms, identifying the risk factors and epidemiology is essential to develop control and prevention planning.

Anaplasma phagocytophilum, Nested-PCR, risk factors, sheep, ۱۶S rRNA