Prevalence and risk factors for Anaplasma marginale seropositivity in cattle in California

Abstract

Bovine anaplasmosis, a tick-borne disease caused by Anaplasma marginale, imposes considerable economic bur­den on cattle industries throughout the world. Clinical signs of bovine anaplasmosis include fever, weight loss, lethargy, jaundice, abortion and death. The severity of the disease in­creases with age, and calves under 1 year of age generally do not progress to clinical disease or develop mild disease. Once infected, cattle remain persistently infected carriers for life. Climate change and drought conditions may affect the distri­bution and prevalence of tick populations and tick-borne dis­eases and re-evaluating the seroprevalence of Anaplasma would provide a better understanding of the disease dynamics in California. To our knowledge, there has been no updated study regarding the distribution of Anaplasma infection status in California since 2008, and the information on weather factors related to the disease is also limited. There is an urgent need to evaluate the prevalence of Anaplasma infection in different regions of California. The goal of this study is to estimate the seroprevalence of Anaplasma infection in California cattle over time, and the specific goal is to identify potential risk factors for infection including animal demographics, region, Anaplasma seroprevalence of wild ruminants, Dermacentor tick species presence, and weather effects.