Heartwater, also known as Cowdriosis, is a tick-borne disease of ruminants caused by the rickettsial organism Ehrlichia cowdriatum. The organism was formerly called Cowdria ruminatum, but the results of molecular studies precipitated the name change. It is transmitted by ticks of the genus Amblyommaand occurs in parts of Africa, some islands in the Indian Ocean as well as some islands in the eastern Caribbean.
In the 1990’s there was a concerted effort to eradicate Amblyomma ticks from the Eastern Caribbean and, as a result halt the spread of Heartwater which had been introduced to the region by some unknown means. The programme involved the use of the acaricide flumethrin (Bayticol®) at specified intervals on all ruminant species. There was also research into the migratory patterns of the Cattle Egret (Bubulcus ibis) which had been shown to transport nymphal stages of the tick, an could therefore spread it between the islands. It was unsuccessful in eliminating the tick, but at this time Heartwater appears to be confined to the islands of Antigua and Guadeloupe3 where the principal transmitting species is the Tropical Bont tick A. variegatum.
Heartwater is a serious, life-threatening illness affecting domestic and wild ruminants. Among the domestics, goats are most susceptible. Clinical signs may vary in severity from peracute to sub-acute and include respiratory distress, collapse, neurological signs such as opisthotonus and paddling. Death may occur in hours to days in the peracute or acute forms, while animals with the less severe form may undergo a long recovery.
Post mortem gross lesions of note include pleural and pericardial effusion (fluid in the chest and around the heart) which clots rapidly on contact with air, pulmonary edema and intestinal congestion. Smears of brain tissue may be examined for organisms and their presence is considered diagnostic.
If caught early, treatment can be effective. Tetracyclines such as Oxytetracycline, Chlortetracycline and Doxycycline may be used along with other supportive measures.
Heartwater has not been diagnosed in Jamaica, but as usual, the veterinary community must maintain vigilance as ticks are very capable of stowing away on the bodies of migrating birds. A recently published paper documents the discovery of Amblyomma dissimile ticks – normally resident in Central and South America and the Caribbean - on a migratory songbird in Canada4.
For more dtailed information on Heartwater, Please click on the references below:
An aborted bovine foetus. Neospora caninum infections in cattle may result in abortion. Photo courtesy of www.nadis.org.uk.
Neospora caninum is a protozoan cyst forming apicomplexan parasite that causes neosporosis, notably in cattle (Bos taurus) and domestic dogs (Canis familiaris). It is closely related to Toxoplasma gondii and has emerged as a major cause of reproductive failure in cattle world-wide. (A)
Neospora caninum is regarded as one of the most important infectious causes of abortion in cattle worldwide, yet there are no definitive studies that quantify losses due to neosporosis in the cattle industry; however, losses are estimated to be in the millions of dollars per year. The two major routes of N. caninum transmission are horizontal, where cattle ingest sporulated N. caninum oocysts and vertical transmission, which includes transmission of the agent to the foetus during pregnancy, either following reactivation of bradyzoites in the infected dam or de novo infection of the dam during pregnancy. (A)
Infection in dogs is generally acquired by consumption of bradyzoite-containing cattle tissues, particularly placenta and foetal membranes. Vertical transmission to puppies in utero may also occur. Clinical disease, including neorological signs and paralysis, tends to occur in puppies under 6-months of age. There is no definitive treatment, although control is best attempted before the onset of severe neurological signs, clindamycin or trimethoprim-sulpha preparations being the drugs of choice. (C)
Unlike it's feline counterpart Toxoplasma gondii, Neospora caninum is NOT known to affect humans.
A - For details on Bovine Neosporosis please click HERE for Dr. Patrick Craig's article "Neospora Caninum and Neosporosis".
B - Click HERE to read Dr. Craig's abstract for his PhD thesis: "The effects of the abortifacient parasite, Neospora caninum on bovine foetuses in early and late gestation." .
C - Click HERE for more details on Canine Neosporosis.