Epidemiological aspects of cattle tick fever in Brazil

Abstract

The present work reviews the epidemiologic situation of Anaplasma marginale and Babesia spp. infections and the occurrence of cattle tick fever outbreaks in Brazil. In areas of tick fever enzootic instability, environmental conditions interfere with the development of Rhipicephalus (Boophilus) microplus: chilly winter in the southern region, floods in the Pantanal, and low humidity in the Caatinga. In contrast, the climatic conditions of stable zones (Cerrado, Amazon and Atlantic Forest biomes) favor tick development. In enzootic areas, tick fever is uncommon because the animals are in frequent contact with the parasite, acquiring immunity naturally during the period of innate resistance; however, outbreaks may occur when calves become infested by considerable numbers of infected ticks during this period or in adults raised in tick-free environments that become infested for the first time when transporting to stable areas. It is necessary to better understand the disease’s risk factors under stable conditions and the implications of the mechanical and other vector transmission of A. marginale. To prevent tick fever outbreaks in Brazil, it is important to develop and use anaplasmosis and babesiosis vaccines in cattle from enzootic unstable regions, especially when animals are moved to stable areas.

The Occurrence of Cattle Tick Fever in a Region of the Atlantic Forest on the Border with the Caatinga in Brazil

“…Previous studies in cattle from the Atlantic Forest biome in the State of Bahia reported high rates of infection with A. marginale and Babesia spp. transmitted by ticks [25], so this region has been identified as an endemic area [11,26]. Despite this, our study found a high frequency of tick fever.…”

“…In the Atlantic Forest, the climatic conditions are optimal for tick development and, consequently, A. marginale and Babesia spp. circulate among animals frequently [11], with the persistently infected animals being the source of infection [27]. Cattle moved from the Caatinga biome to the Atlantic Forest biome may be susceptible to tick fever because they come from an area with few or no ticks and, consequently, they may have low levels of antibodies against A. marginale and/or Babesia spp.…”

“…[10]. The Caatinga biome in Brazil was previously categorized as an area of enzootic instability for cattle tick fever because the low humidity impairs tick development [11]. A disease is considered endemic if it is more frequent in older individuals than in younger ones and if the initial infection reduces the probability that subsequent infections result in acute presentations [12].…”

“…A disease is considered endemic if it is more frequent in older individuals than in younger ones and if the initial infection reduces the probability that subsequent infections result in acute presentations [12]. This stable tick fever situation has been documented in the Atlantic Forest biome in Brazil, where the environmental conditions are ideal for tick development [11]. The occurrence of cattle tick fever may be higher in the border region between the Caatinga and the Atlantic Forest biomes due to animal movement, limited surveillance, and poor management conditions.…”

“…Tick fever can cause high economic losses because of mortality, weight losses, subclinical productive losses, and the cost of treatments. In the State of Rio Grande do Sul, an important region for the production of livestock which is commonly perceived to have enzootic instability for cattle tick fever [11], the disease causes losses due to mortality, which is estimated at 1.6 million dollars annually [13].…”