The Nematodes Thelazia gulosa Railiet and Henry, 1910 and Thelazia skrjabini Erschov, 1928 as a Cause of Blindness in European Bison (Bison bonasus) in Poland

Abstract

Purpose The nematodes of the genus Thelazia are the cause of eye diseases of wild and domestic ruminants throughout the world. The aim of the study was to describe clinical cases of thelasiosis in European bison (Bison bonasus) in Poland, and provide morphometrical features of Thelazia gulosa Railiet and Henry, 1910 and Thelazia skrjabini Erschov, 1928 regarded as potentially useful for species differentiation Methods The conjunctival sacs, tear ducts, the surface of the cornea and nicitating membrane collected from bison were rinsed with saline solution. Any nematodes isolated from the sediment were subjected to morphometric analysis. Results Thirteen of the 16 examined European bison were infected with Thelazia nematodes, belonging to the species T. gulosa and T. skrjabini. The intensity of infection ranged from one to six (mean intensity 5), and four to 29 (mean intensity 14) nematodes T. skrjabini and T. gulosa respectively. Congestion of conjunctival sac, keratitis and corneal opacity, corneal ulceration and perforation as well as purulent eyeball inflammation were observed in infected animals. Conclusions Thelazia gulosa and T. skrjabini can be identified by morphometrical features. As thelasiosis might be a serious threat for protected population of European bison, further studies are needed of the epidemiology and pathology of this emerging parasitosis in Poland.

Human–Wildlife Conflict: The Human Dimension of European Bison Conservation in the Bieszczady Mountains (Poland)

“…So, it would appear that the surveyed Rzeszów inhabitants’ opinions on European bison were based mainly on common knowledge about this species; these results are similar to those of Herman et al’s [ 50 ] studies on the attitudes of students towards European bison and wolves in Germany. Evidence for this is the fact that city respondents felt that the greatest threat posed by the bison was to public health ( Table 1 ), which has nothing to do with the actual data on the damage and threats caused by wisents in the Bieszczady Mountains [ 33 ]. The actual and most common problems for local residents (such as economic losses or forest use restrictions) are little known to urban respondents (they very rarely indicated them as significant in the survey).…”

“…Currently, the Bieszczady Mountains is home to over 660 animals; this not only the second largest European bison population in the world (after the Białowieża Forest population), but it is also the largest population of the lowland–Caucasian line [ 3 ]. Given the past and present threats of infectious diseases, this high density is risky [ 32 , 33 ]. Social acceptance may also be an important limitation for further population development.…”

European Union needs urgent strategy for the European bison

“…in total) (Raczyński, 2022). The future of the European bison population in Poland is also uncertain due to threats of diseases, for example, telaziosis, which may cause a significant decrease in the population numbers in Bieszczady (Demiaszkiewicz et al., 2020), the largest population of Lowland‐Caucasian line in Europe. In addition, some of populations are overcrowded, which increases the risk of disease transmission and exposes the European bison to other threats like intensified migration toward agriculture and build up areas.…”

The occurrence and molecular identification of Thelazia spp. in European bison (Bison bonasus) in the Bieszczady Mountains

“…Thelazia lacrymalis and T. rhodesi have also been isolated from the eyeballs of a horse 7,10 .Adult nematodes localize in the conjunctival sac and tear ducts, under the nictitating membrane and on the cornea of infected animals 6,7 . The eye worms are transmitted by secretophagous non-biting flies from the genus Musca, which become infected with the first stage larvae while feeding on animal lacrimal secretions 6,11 . In the intermediate host, the first-stage larvae develop into the invasive third stage, migrate to the fly suckers and are…”

“…The pathogenic effect of Thelazia nematodes derives from the mechanical irritation of the conjunctiva and cornea, as well as the toxic effect of parasitic metabolites. The infected animals suffer from acute conjunctivitis, often complicated by secondary bacterial infections leading to purulent eye inflammation, corneal opacity, and ulceration 6,8 .…”