Anaplasmosis

• Bovine Anaplasmosis is also known as gall sickness and is caused by obligate intraerythrocytic bacteria of the order Rickettsiales, family Anaplasmataceae, genus Anaplasma.
• Cattle, sheep, goats, buffalo and some wild ruminants can be infected with Bovine Anaplasmosis.
• Bovine Anaplasmosis occurs in tropical and subtropical regions worldwide, including South and Central America, the USA, southern Europe, Africa, Asia, and Australia.
• Clinical bovine anaplasmosis is usually caused by A marginale.
• A centrale was isolated in South Africa from cattle with a mild disease.
• A phagocytophilum has recently been reported to infect cattle; however, natural infection is rare and it does not cause clinical disease.
• In the Philippines, A marginale is prevalent in the southern part of Luzon (Rhiphicephalus microplus).
• There are various tick vector species of anaplasma, with 17 being the most common.
• Rhipicephalus (Boophilus) spp are major vectors of A marginale in Australia and Africa.
• Chronic infections usually occur in animals that survive the initial disease and become carriers of the disease.
• Haemoglobinaemia and haemoglobinuria are not present in bovine anaplasmosis.
• Brown urine is a symptom of bovine anaplasmosis, but hemoglobunuria does not occur.
• Diagnosis of bovine anaplasmosis can be done through microscopic examination of stained blood smears using Wright’s stain, New Methylene Blue, Giemsa stain, serological method, polymerase chain reaction (PCR), and post-mortem examination or Necropsy.
• Treatment and prevention of bovine anaplasmosis include tetracycline antibiotics and imidocarb, blood transfusions, vaccination, and prevention measures such as insect control, sanitizing needles and instruments between individual animals, and reducing the severity of clinical signs in newly infected animals.
• Chronic stages of bovine anaplasmosis include acute infection and gradual emaciation.
• Dermacentor spp are the main vectors in the USA.
• Clinical signs of bovine anaplasmosis include icterus, thin and watery blood, splenomegaly, hepatomegaly with yellow-orange discoloration, and pericardial petechiae.
• Mechanical transmission via biting insects occurs in some regions.
• Anaplasmosis may also be spread through the use of contaminated needles or dehorning or other surgical instruments (castration instruments).
• Transplacental: Spread from the dam to the fetus via the placenta is possible when the dam is infected during the second and third trimesters of pregnancy.
• Anaplasmosis starts when the Anaplasma, the causative agent of this disease, infects the herd through the bite of infected insects such as ticks, horse flies, or horn flies.
• The spread of infection can also be due to instruments that are not disinfected between animals e.g needles or even transplacental infection.
• Once the bacteria enter the body, they will multiply in the bloodstream, invade and attach to the red blood cells.
• This attachment will cause changes in the erythrocyte and the bacteria will be detected by the IgG since it is found in the blood circulation.
• This will trigger the immune system to develop antibodies to circulating RBCs leading to hemolysis (immune-mediated extravascular hemolysis) or rupture of RBCs.
• Eventually, due to hemolysis, red blood cells are destroyed faster than the body can produce resulting in anemia, the hallmark sign of anaplasmosis.
• In some instances, cattle may become carriers.
• Carrier means that they harbor organisms in the bloodstream and are capable of spreading the disease but do not show signs of anaplasmosis.
• This happens when the cattle recover from the disease thus, they remain chronically infected carriers but they are generally immune to further clinical disease.
• Recovered animals possess lifelong immunity.
• Clinical findings of Bovine Anaplasmosis include all ages of cattle being susceptible, with younger cattle, especially less than 6 months old, rarely exhibiting signs of disease due to rapid and active production of new red blood cells in growing calves.
• Anaplasmosis is characterized by progressive anemia due to extravascular destruction of infected and uninfected erythrocytes.
• Bovine Anaplasmosis occurs in several forms: peracute (most severe, but rare), acute and chronic.