Project Overview

Reports

Commodities

• Animals: bovine

• Human Health: workers, residents, applicators

• Natural Areas: wildlife

Target Pests

• Target Pests: ticks

Practices

• Pest Management: disease vectors, monitoring/scouting

• Animal Production: animal protection and health, parasite control

• Natural Resources/Environment: wildlife

Anaplasmosis is a disease of livestock, wildlife, and humans caused by several species of rickettsial intracellular bacteria in the genus, Anaplasma. In cattle, anaplasmosis is caused by A. marginale, which is naturally transmitted by the bite of infected ticks, particularly Dermacentor species. Older animals are more susceptible to the pathogen and exhibit more severe clinical disease. Acute infections are characterized by anemia resulting from the destruction of red blood cells, and up to 30% mortality. White tailed deer in the United States are also commonly infected with A. phagocytophilum, the causative agent of human anaplasmosis, when fed upon by adult Ixodes scapularis ticks, and serve as an important reservoir host for pathogen maintenance. Additionally, a number of countries have recently reported cases of A. phagocytophilum in cattle, suggesting the potential for livestock to also serve as a reservoir host. Anaplasma phagocytophilum-positive cattle have not yet been reported from the United States, but the possibility of infection should be considered an emerging concern.

In the southern US, bovine anaplasmosis is a significant concern for cattle producers. In Arkansas, A. marginale is widespread in beef herds, with one recent study finding a seroprevalence rate of over 58%. Seroprevalence rates are similarly high in other southern states, like Tennessee and Kentucky, where determination of the association between the abundance and species composition of blood feeding arthropods and anaplasmosis incidence in cattle is a PMSP research priority. Despite the extremely high burden of anaplasmosis in Arkansas cattle, few Dermacentor ticks are typically collected off of animals or in pastures in the southeast. Instead, these collections tend to be dominated by Amblyomma americanum, the lone star tick, which is not associated with Anaplasma transmission. The apparent lack of competent A. marginale vectors in the southeastern US has confounded attempts to clarify the primary natural transmission cycle in enzootic areas. Studies that have attempted to assess the prevalence of A. marginale in livestock-associated ticks have concluded that increased surveillance is needed to accurately assess the role of certain tick species in transmission. In Arkansas, tick collections made on cattle and cattle operations during spring-fall 2020 revealed a number of livestock associated species, including the known A. marginale vector, D. variabilis and the known A. phagocytophilum vector, I. scapularis. As recent regulatory changes have removed over the counter antibiotic mineral feeds from stores that were commonly used by producers to manage anaplasmosis in herds, knowledge of which tick species are involved in Anaplasma transmission in the southeast US is critical to developing IPM strategies for anaplasmosis prevention.

The proposed research will assess the risk of anaplasmosis caused by A. marginale and A. phagocytophilum to Arkansas cattle by a) screening previously collected tick samples for these pathogens to determine which species are involved in Anaplasma transmission and the pathogen prevalence in vectors, b) collecting ticks from properties where Anaplasma-positive ticks were collected in 2020 to determine whether the pathogen is maintained interseasonally on a small scale, and c) screening ticks opportunistically collected from hunter-killed deer to determine whether there is a risk of ticks moving these pathogens between wildlife and livestock. Additionally, we will survey Arkansas cattle producers on their knowledge of and attitudes towards tick control to understand current integrated pest management practices in use for tick and tick-borne disease control in Arkansas. Survey data will allow us to assess whether current control practices are likely to be effective for anaplasmosis prevention based on the results of our study, and will serve as a baseline to measure future changes in practices resulting from study objectives.