Thelaziosis in Wisents of the Shahdag National Park (Azerbaijan)

Abstract

In the Shahdag National Park (Azerbaijan) the natural grouping of wisents (European bisons) is being formed. The program should eventually result in obtaining the independent stable grouping of wisents, capable of existing and reproduction without human interference. In the course of work with the grouping such a disease as wisent thelaziosis was detected. The presence of the disease can negatively affect the efficiency of the wisents reintroduction program. The aim of the work was to identify the problem, describe the clinical cases of wisent thelaziosis and determine possible measures to minimize risks for animals health. The article presents the data collected throughout a three years period of wisent group formation. The diagnosis – thelaziosis – was confirmed by finding the mature thelazia specimens of Thelazia rhodesi species. Such clinical manifestations as photophobia, eyelid edema, pathological lacrimation, serous conjunctivitis, purulent-catarrhal keratoconjunctivitis, clouding and ulceration of the cornea up to perforating ulcers, iridocyclitis were observed in wisents. The clinical form of thelaziosis had been detected in a wisent herd at all seasons of the year, at maximum in the period from the end of May to the end of July, up to 18.8 % of animals in the herd. At the rest of the time, the percentage of animals with disease manifestation varied from 3.7 to 11 %; two years in a row the cases of disease manifestation in adult wisents were observed in February. One case of thelaziosis was registered in a 1.5-month-old calf, the disease evolved in a hyperacute form. For treatment against thelaziosis in wisents the single intramuscular injections of ivermectin at a dose of 200 μg/kg (Ivermec, 2 ml/100 kg) were used. Medical treatment was given frontally to the herd after each detected clinical case. In addition wisents with strongly expressed clinical signs received a single injection of tulathromycin at a dose of 2.5 mg/1 kg (Draxin, 2.5 ml/100 kg). Medications were injected by means of a remote gun Dan-Inject. In Azerbaijan thelaziosis is spread among productive animals, as evidenced by veterinary reports. However, systematic studies of thelaziosis were carried out only in the 70–80s. As follows from the studies the thelaziosis infection rate in Azerbaijan has clearly expressed zonal distribution: high infection rate in the plain and submontane zones and rare cases of disease occurrence in the mountain belt. It was concluded that when forming wisents population, it is necessary to take into account the factor of zonality and plan the populations’ release in the mountainous areas of the national park, as the safest from veterinary side. Also due to domestic animals being the main source of infection for wisents in Azerbaijan, it is necessary to conduct research on disease expansion and intensity of infection in domestic livestock in the areas bordering with the Shahdag National Park. Currently while wisents are kept at the quarantine and transfer place, given the proximity of the enzootic focus, it is recommended to conduct the systematic frontal preventive treatment with ivermectin.