Babesiosis

Babesiosis a disease of domestic and wild animals characterised by extensive erythrocytes lysis leading to anaemia, jaundice, and haemoglobinuria (red blood pigment in urine).

The disease caused by ptotozoan parasites of the genus Babesia is transmitted by a variety of tick species. Babesia is a pyriform protozoan measuring 2-5 B5m in length which infects the Red Blood Corpuscles (RBC) of affected animals. There are at least 14 distinct species of Babesia which have been recorded in various vertebrate hosts distributed throughout North and South America, Europe, Africa, Australia and Asia. Babesia species that infect animals in Bangladesh are: Babesia bigemina frequently infecting cattle above 2 years of age; incidence is around 0.3 percent in the country. Only on a few occasions it has been reported from buffaloes. B. bovis is also sporadically reported from cattle. Tick Boophilus microplus has been identified as the vector of both B. bigemina and B. bovis; transmission is always trans-ovarian, ie protozoans when ingested by the engorging female passes to the ovary, then to the ova/eggs. The larvae hatching out of the eggs infest a new host, and transferring the protozoans to it.

Both Babesia motasi and B. ovis have been sporadically recorded in sheep and goats in Bangladesh. The ticks Haemaphysalis bispinosa and Rhipicephalus sanguineus are implicated as vectors.

Babesia equi has been recorded in horses and donkeys in Bangladesh. The known vector is R. sanguineus. In dogs Babesia gibsoni and B. canis have been reported in the country. Although there is little documentation about their incidence, babesiosis has been very frequently encountered in dogs by pet animals practitioners. Ticks which act as vectors are R. sanguineus and Haemaphysalis bispinosa respectively for B. gibsoni and B. canis.

In babesiosis the pathogens invade the RBC of infected animals and causes severe destruction of the RBC. The onset of the disease within 2-7 days of infection is acute in most animals and is associated with rise of body temperature and coffee coloured urine due to release of heamoglobin from destruction of about 70 percent of the RBC within two to seven days of infection; fatality is common if treatment is not given within 2-3 days of the onset of symptoms. Young animals such as calves, lambs, kids, and young horses are not susceptible to babesiosis. Dogs of all age groups are equally susceptible to babesiosis, and puppies being more susceptible than adults. [M Hafizur Rahman] [Rahman, M Hafezur Professor of Parasitology, Bangladesh Agricultural University]