Control Of Bovine Anaplasmosis Research Articles

Molecular Epidemiology and Risk Factors Assessment of Anaplasma spp. on Dairy Cattle in Southwest of Iran

DOI : 10.26650/actavet.2019.18014 The present study was carried out to determine Anaplasma species and potential risk factors associated with molecular prevalence of Anaplasma spp. among dairy cattle in southwest of Iran. A total of 88 samples out of 200 generated an expected amplicon of 866 bp from Anaplasma marginale msp4 gene. Six samples that were identified as A. marginale gave also positive results for A. phagocytophilum 16S rRNA gene with specific nested polymerase chain reaction (nPCR). The multivariate analysis of risk factors revealed that the cattle of mountain regions were significantly (p=0.0001) at higher risk as compared to the plain regions. Cattle <1 year age and the latitude 32-33°C were significantly at lower risk (p<0.01). The cattle with low milk yield were significantly (p=0.002) at lower risk. Low hygienic farms were significantly (p=0.011) at higher risk as compared to good and normal hygienic farms. Distance from other farms (<1Km) was another important risk factor which showed significant association with the occurrence of Anaplasma infection (p=0.021). The results of this study can be used in strategic planning for prevention and control of bovine anaplasmosis in dairy cattle in the southwest of Iran.

Current challenges in the diagnosis and control of bovine anaplasmosis

Bovine anaplasmosis, caused by the intracellular rickettsia Anaplasma marginale, continues to impact cattle production in the US. Control and management of bovine anaplasmosis is influenced by our understanding of the complexity of this pathogen, interactions with both cattle and tick hosts, and the disease. A. marginale is maintained in nature through biological transmission by ticks and mechanical transmission by any means of blood transfer from infected to susceptible cattle. The major surface protein 5 (MSP5)-based cELISA, approved for use in the US and Canada, has proven to be a sensitive serologic test. However, more recently this test has been shown to be cross-reactive with closely related organisms, including A. phagocytophilum, because of the conservation of MSP5. Therefore, additional molecular tests may be required in some situations to confirm the identity of the infective agent. While tetracycline antimicrobials are approved by the US Food and Drug Administration for prevention or treatment of acute anaplasmosis, no antimicrobials are labeled for elimination of persistent A. marginale infection. Administration of tetracyclines is an important means of preventing clinical anaplasmosis, but does not prevent cattle from becoming infected with A. marginale. The mode of action of tetracycline is bacteriostatic rather than bactericidal, and its long-term use does not consistently clear cattle of persistent A. marginale infections. USDA approved vaccines for anaplasmosis are currently unavailable. The challenges of vaccine development include the antigenic variation of A. marginale that occurs during persistent infections and the increased antigenic diversity of A. marginale strains, especially in areas of ongoing cattle movement. The overall goal of this and a previous overview is to summarize the current status of knowledge and research on bovine anaplasmosis, and to provide veterinarians with answers to frequently asked questions.

Current challenges of the management and epidemiology of bovine anaplasmosis

Bovine anaplasmosis, caused by the intracellular rickettsia Anaplasma marginale, is endemic in several areas of the United States and has continued to impact cattle production. While considerable research has been done over the past several decades, control strategies for anaplasmosis have advanced minimally since the first anaplasmosis vaccine was marketed in the US in the 1960s. However, these research findings have continued to contribute to our overall understanding of the complexity of bovine anaplasmosis. With the advent of molecular biology, host/pathogen interactions are currently better defined and the classification of Anaplasma has been reorganized to include several organisms in addition to those that are host-specific for ruminants. In this review, the current status of anaplasmosis is discussed with the aim of providing insight to bovine practitioners on the future challenges for the management, diagnosis, and control of bovine anaplasmosis. This review focuses on updated information on the classification of the genus Anaplasma and related organisms, the developmental cycle of A. marginale in cattle and ticks, the role of male ticks in transmission of anaplasmosis, the diversity of A. marginale strains, the wildlife reservoirs of A. marginale, and the potential influence of climate change on the epidemiology of this serious disease. A second review will follow which focuses on current issues related to diagnosis and control of bovine anaplasmosis. Overall, the goal of these reviews is to provide an understanding of the current status of research and knowledge of bovine anaplasmosis and provide veterinarians answers to frequently asked questions.