Anaplasmosis
Anaplasmosis in cattle is an infectious disease caused by bacteria of the genus Anaplasma spp, which invades the red blood cells of cattle.
This disease is present in tropical and subtropical regions of the world, and is not limited to cattle, but also affects buffalo, deer, and antelope. In Mexico, the disease is caused by the Anaplasma marginale species and is considered endemic.
Clinical signs
Clinical manifestations appear after a variable incubation period, which can range from 7 to 60 days, or until 15% of red blood cells are infected.
Once the bacteria invade red blood cells, they replicate rapidly during an acute phase characterized by high fever and weakness. The destruction of infected cells causes severe anemia. Other signs of the disease include yellowing of the mucous membranes, lethargy, abortions, and sometimes death.
The severity of the disease is closely related to the age of the infected animal. Cattle under 6 months of age show almost no clinical signs; animals between 6 months and 1 year of age become mildly ill; animals 1 to 2 years of age suffer an acute but rarely fatal illness, while the disease is most fatal for animals older than 2 years.
Transmission
Anaplasmosis is transmitted in different ways, including biological and mechanical routes.
The biological pathway is considered of great importance, as it involves the bite of Rhipicephalus (Boophilus), Amblyomma, and Dermacentor ticks. In this mechanism, the bacteria multiply in the ticks' intestines and salivary glands, enabling transmission when the tick feeds on bovine blood.
The mechanical route includes transmission by other vectors, such as the stable fly (Stomoxys calcitrans) and flies of the genus Tabanus spp. Another possible form of mechanical transmission is when cattle become infected after using contaminated instruments, such as needles and dehorning material.
Disease management
This disease is suspected when animals older than one year present acute fever, signs of anemia, and jaundice (yellowing). Other related factors are environmental, as the prevalence of the disease is higher during the rainy season and when potential vectors are present.
Although animals can recover from clinical disease, it is important to confirm the diagnosis of anaplasmosis, as animals can have a chronic infection and be lifelong carriers of the bacteria.
It is also vital not to administer antibiotic treatment until the diagnosis is confirmed and the presence of other diseases, such as babesiosis, has been ruled out.