The Pathology of Pathogenic Theileriosis in African Wild Artiodactyls

Abstract

The published literature on schizont-“transforming,” or pathogenic theileriosis, in African wild artiodactyls is dated and based on limited information. Here the authors review the taxonomy, diagnosis, epidemiology, hematology, pathology, and aspects of control in various species. Molecular studies based on 18S and 16S rRNA gene sequences have shown that African wild artiodactyls are commonly infected with diverse Theileria spp., as well as nontheilerial hemoprotozoa and rickettsia-like bacteria, and coinfections with pathogenic and nonpathogenic Theileria species are often recorded. Although theileriosis is still confusingly referred to as cytauxzoonosis in many species, the validity of a separate Cytauxzoon genus in artiodactyls is debated. The epidemiology of theileriosis is complex; the likelihood of fatal disease depends on the interplay of parasite, vertebrate host, tick vector, and environmental factors. Roan calves ( Hippotragus equinus) and stressed animals of all host species are more susceptible to fatal theileriosis. Even though regenerative anemia is common, peripheral blood piroplasm parasitemia does not correlate with disease severity. Other than anemia, common macroscopic lesions include icterus, hemorrhages (mucosal, serosal, and tissue), fluid effusions into body cavities, lung edema, and variably sized raised cream-colored foci of leukocyte infiltration in multiple organs. Histopathologic findings include vasocentric hyperproliferation and lysis of atypical leukocytes with associated intracellular schizonts, parenchymal necrosis, hemorrhage, thromboembolism, and edema. Immunophenotyping is required to establish the identity of the schizont-transformed leukocytes in wild ungulates. Throughout the review, we propose avenues for future research by comparing existing knowledge on selected aspects of theileriosis in domestic livestock with that in African wild artiodactyls.

Pathological findings in African buffaloes (Syncerus caffer) in South Africa

“…The appearance of tuberculous lesions and those of theileriosis corresponded to previous reports in buffaloes (Bengis et al 1996 ; Clift et al 2020 ; De Vos et al 2001 ; Laisse et al 2011 ). Sarcocyst morphology was consistent with Sarcocystis cafferi as previously reported in African buffaloes (Dubey et al 2014 ; Quant et al 1997 ) and occurred only in free-ranging buffaloes presumably because, in such animals, predators are present to complete the indirect life cycle.…”

Bovine Cerebral Theileriosis: First Molecular Confirmed Report in Cross Bred Cattle Calf in India

“…Possible trophism of the parasite towards the central nervous system leads to lesion in endothelium responsible for lymphoblastic accumulation and venous thrombi (Bader et al 1986). However, the severity of theileriosis depends on the inter play of parasite, vertebrate host, tick vector and environmental factors (Clift et al 2020).…”

Theileria, Hepatozoon and Taenia infection in great gerbils (Rhombomys opimus) in northwestern China

“…Among the others, members of the genus Theileria may infect white-tailed deer ( Odocoileus virginianus ), cheetahs ( Acinonyx jubatus ), wild sika deer ( Cervus nippon yesoensis ), red deer ( Cervus elaphus ), wild Chinese water deer ( Hydropotes inermis argyropus ), wild boar ( Sus scrofa ), red fox ( Vulpes vulpes ), zebra ( Equus quagga ), and wild donkey ( Equus africanus ) ( Tirosh-Levy et al, 2020 ). Symptoms of affected wildlife include icterus, splenomegaly and lymphadenomegaly ( Clift et al, 2020 ).…”