Anaplasmosis

Ruminants: fever, loss of appetite, pale then yellow mucous membranes, weakness, rapid weight and milk loss, abortion and sometimes sudden death in adult cattle; A. ovis infection in small ruminants is usually subclinical but can cause fever, severe anaemia, weight loss, reduced milk and abortion. Dogs: fever, lethargy, anorexia, enlarged lymph nodes, pale gums, pinpoint bruising and nosebleeds from low platelets. At necropsy in cattle the carcass is anaemic and jaundiced with an enlarged spleen and distended gallbladder.

Anaplasmosis is a group of tick-borne infections caused by obligate intracellular bacteria of the genus Anaplasma (order Rickettsiales), and the species determines which blood cell is attacked. Anaplasma marginale in cattle and A. ovis in sheep and goats live inside red blood cells; the body clears infected and uninfected red cells outside the circulation, producing progressive anaemia and, in cattle, jaundice. A. platys infects platelets in dogs, causing cyclic drops in platelet count through direct damage and immune-mediated destruction. A. phagocytophilum infects neutrophils, lowering white cell and platelet counts in dogs, horses, ruminants and people. Survivors of red-cell infection commonly remain carriers.

Anaplasma species occur worldwide, especially in tropical and subtropical regions. Ticks are the main vectors: Rhipicephalus and Dermacentor for A. marginale, Rhipicephalus sanguineus for A. platys in dogs and for A. ovis in central Tunisia, and Ixodes ticks for A. phagocytophilum. Biting flies, other insects, reused needles and instruments spread red-cell species mechanically, and transplacental infection is reported. In central Tunisia A. ovis was found in every ewe tested at the first visit and infection built up in lambs over the warm season; in northern Algeria A. marginale was found in 4.0% of 299 clinically ill cattle examined at clinics, peaking in July. A. phagocytophilum and A. platys are zoonotic, with human cases recorded, while A. marginale has not been reported in people. Severity in cattle increases with age.

In ruminants, babesiosis (causes haemoglobin in urine, which anaplasmosis does not), theileriosis and leptospirosis. In dogs, ehrlichiosis caused by Ehrlichia canis, babesiosis caused by Babesia vogeli and Lyme borreliosis, which often occur as co-infections spread by the same ticks. Confirmation rests on seeing the organism in stained blood smears (inclusions in red cells, platelets or neutrophils), serology or PCR, with sequencing to name the species.

Blood (red blood cells, platelets, neutrophils), spleen, liver, gallbladder, lymph nodes, mucous membranes, reproductive tract

Tick control with acaricides during the transmission season, biting-fly control, a new or sterilised needle for every animal, testing animals before they join a herd, and live A. centrale vaccination of calves where permitted.

Most young ruminants recover and become carriers; untreated newly infected adult cattle may suffer 30-50% mortality (Illinois Extension). Tetracyclines are the main treatment class in animals and people and work best when started early.