Presently, small ruminant farming has become very lucrative and is playing a significant role in uplifting the socio-economic status of the poor and marginalised farmers in India. Parasitism is considered as important risk factor for the production of small ruminants and causes huge economic losses in most of the developing and underdeveloped parts of the world. Parasitic diseases are regarded as a major constraint to animal productivity worldwide¹. Amongst the different parasites infecting ruminants, vector borne parasitic diseases significantly affect the health of animals resulting in anaemia, which eventually leads to reduced production and productivity².

Theileriosis is an important tick-borne hemoprotozoan disease that can reduce the productivity, which results into severe economic losses in goat farming³. Although, the disease was mentioned to affect small ruminants, it was less studied particularly in goats. Among the various species of Theileria that infect small ruminants in tropical and sub-tropical countries including India, T. uilenbergi, T. lestoquardi and T. luwenshuni are considered as highly pathogenic in sheep and goats^4,5,6.

Though bovine theileriosis has been extensively studied in the Indian subcontinent, there is a paucity of information on haemoprotozoan diseases occurring in Indian small ruminants in general as well as on ovine or caprine theileriosis^7,8. Hence, the present study was designed to study the clinical profile, haemato-biochemical and pathological changes of theileriosis in goats.

The present study was conducted at Department of Veterinary Pathology, College of Veterinary and Animal Sciences (COVAS), Udgir, Maharashtra on 107 cases mainly comprising local Osmanabadi breed goats of all ages and both sexes with the history of fever, swollen lymph nodes, pale mucous membranes and tick infestation, which were admitted to Teaching Veterinary Clinical Complex and reported from areas in and around Udgir city of Maharashtra state during period January to December 2020.

The blood samples for analysing various haematological and biochemical parameters were collected from suspected goats (n=107) under aseptic condition from jugular vein in ethylenediamine tetraacetic acid (EDTA) and clot activator vacutainers respectively. The haematological parameters haemoglobin (Hb), packed cell volume (PCV), total erythrocyte count (TEC) and total leukocyte count (TLC) were estimated manually. The differential leucocyte count (DLC) was estimated from Giemsa-stained blood smears. The serum biochemical parameters such as total bilirubin, aspartate aminotransferase (AST), alanine transaminase (ALT), blood urea nitrogen (BUN), creatinine, calcium and phosphorus were analysed on semi-automated biochemical analyser (Micro LAB, versatile Bio-chemistry analyzer, Model: RX-50V) by using standard commercial biochemical kits supplied by ARKRAY Healthcare Pvt. Ltd. For control purpose, the blood samples were collected from healthy goats (n=12) from Livestock Farm, College of Veterinary and Animal Sciences, Udgir of same age, breed and sex.

Thin blood smears were prepared from suspected goats by puncturing ear vein with 20-gauge needle. The prepared blood smears were air dried, fixed with methanol and subjected for Giemsa staining as per routine protocol. The blood smears were considered positive for Theileria spp. on the basis of presence of intra-erythrocytic theilerial piroplasms with morphology such as signet ring/crescent, pyriform/pear, dot/round and rod/bayonet shape.

The fine needle aspirations of swollen prescapular lymph nodes from theileriosis suspected clinical cases were collected by using 20-gauge needle and impression smears of cut open surfaces of lymph nodes during necropsy were obtained from suspected animals. The prepared smears were fixed in methanol and stained by same procedure mentioned above for blood smears. The lymph node aspiration or impression smears were screened for the presence of intra-cytoplasmic schizonts (Koch’s blue bodies) of Theileria spp. to confirm the positivity for theileriosis.

The detailed post-mortem examination of theileriosis positive goat carcasses were conducted and gross lesions observed in various organs/body systems were recorded. For histopathology, the tissue samples of 0.5 cm size from abomasum, lungs, liver, kidneys, spleen, lymph nodes and heart were collected and fixed in 10% neutral buffered formalin. The formalin fixed and paraffin embedded tissue samples were processed and stained with Haematoxylin and Eosin staining method as per standard protocol⁹. The data generated from different parameters of present the study were subjected to independent samples t-test by using IBM SPSS software (version 20) for windows.

Out of 107 suspected cases which were screened for theileriosis, forty-one (n=41) goats were found positive for theileriosis by blood and lymph node aspiration smear examination indicating an overall prevalence of 38.32%.

The theileriosis positive goats showed clinical signs such as fever, pale mucous membranes, swollen lymph nodes, respiratory distress, presence of tick infestation, anorexia and dull or depressed behaviour (Fig. 1 a-d). In few cases, the clinical signs such as lameness, nasal or ocular discharge, diarrhoea, recumbency and corneal opacity were also recorded.

Positive cases (n=41) were confirmed on the basis of presence of intra-erythrocytic signet ring/crescent, pyriform/pear, dot/round and rod/bayonet shaped piroplasm’s of Theileria spp. in blood smears from suspected goats (Fig. 2 a-b). The lymph node aspiration smears from theileriosis positive goats revealed presence of numerous activated lymphoblastoid cells and macrophages with basophilic cytoplasm, frequently idented nuclei, prominent nucleoli and mitotic figure having intra-cytoplasmic schizonts (Koch’s Blue Bodies) confirming the positivity for theileriosis. The extracellular schizonts were also evident in few stained cytological preparations (Fig. 2 c-d).

The haematological analysis of blood samples of theileriosis positive goats (n=41) revealed highly significant increase (P<0.01) in total leucocyte count, relative counts of neutrophils and eosinophils as compared to healthy control goats (n=12). Whereas, highly significant (P<0.01) decrease in total erythrocyte count, haemoglobin concentration and packed cell volume as well as in relative counts of lymphocytes were evident in theileriosis affected goats (Table 1).

Biochemical analysis of serum samples from theileriosis positive goats (n=41) revealed significant increase (P<0.05) in the levels of AST, whereas highly significant increase (P<0.01) in the levels of ALT, total bilirubin, blood urea nitrogen and creatinine as compared to healthy control goats (n=12). On other hand, the highly significant (P<0.01) decrease in serum levels of calcium and phosphorus were observed in theileriosis affected goats (Table 2).

The external examination of carcasses of theileriosis positive goats (n=8) revealed presence of congested, pale or papery white mucous membranes, nasal discharge, swollen lymph nodes and tick infestation. On incision, the lymph nodes of theileriosis affected goats appeared swollen, oedematous and showed cortical hemorrhages intermixed with necrotic foci in few cases (Fig. 3a). Marked splenomegaly was noticed in affected goats along with frequent soft semisolid splenic pulp (Fig. 3b). The abomasal mucosa revealed marked oedema of rugal folds and presence of widespread punched out ulcers with necrotic centres and haemorrhagic borders (Fig. 3 c-d). The livers frequently appeared to have mild to moderate enlargement in addition to mild yellowish-brown discoloration. The petechial to ecchymotic endocardial hemorrhages were also evident in few cases.

Histopathological examination of abomasum from theileriosis positive goats revealed presence of multiple haemorrhagic ulcerations and marked necrosis of mucosal epithelium with marked mononuclear cell infiltration. The denuded necrosed mucosal epithelium of abomasum frequently found trapped in fibrin and adhered to the native mucosal surface appearing as deep eosinophilic masses. Moderate to severe mononuclear cells infiltration was also frequently evident within underlying lamina propria, submucosa and around blood vessels containing fibrin thrombi (Fig. 4 a-d).

The lymph nodes of affected goats showed marked proliferation and dense packing of mononuclear cells within cortex causing loss of normal structure. In few cases, marked cortical edema or infiltration of fibrinoid material and hemorrhages were evident (Fig. 5 a-b). Marked congestion, hemorrhages and hemosiderin deposition was evident in spleen (Fig. 5c). Other changes were similar as observed in lymph nodes. Pulmonary alveolar septae found markedly thickened due to infiltration of mononuclear cells, congestion and hemorrhages (Fig. 5d). Marked edema and emphysema was also observed in few affected goats.

Heart revealed mild to moderate degeneration of myocardial muscle fibres and infiltration mononuclear cells (Fig. 6a). Moderate degree of hepatocellular vacuolar degeneration and fatty changes were evident in liver from affected goats along with moderate to heavy infiltration of mononuclear cells within sinusoids and periportal areas. Marked tubular necrosis, non-suppurative interstitial nephritis and atrophic peri-glomerulitis were observed in kidneys of affected goats (Fig. 6b).

The clinical signs of theileriosis observed in goats of present study were in agreement with the findings reported by earlier research workers^7,8,10,11. Similar to present observations, the prevalence of theileriosis around 36.47% has been reported in goat population from West Bengal, India¹². The findings recorded regarding blood smear and lymph node aspiration cytology in present study were found in consonance with earlier reports_{3,7,8,10,11,13,14,15}.

More or less similar haematological findings of theileriosis in goats were reported by earlier investigators^16,17. Furthermore, these earlier studies^16,17 stated that, the significant increase of total leucocyte, neutrophil and eosinophil counts can be attributed to inflammatory responses against tissue damage and tick infestation in theileriosis affected animals while the decrease in erythrocyte count, haemoglobin concentration and packed cell volume considered due to destruction of erythrocytes containing piroplasm's. Whereas, they correlated decreased lymphocyte count with destruction of lymphocytes due to multiplication of schizont stages of Theileria spp.

The biochemical changes observed in present study were found in consonance with earlier studies of theileriosis in goats^17,18,19,20. The decreased levels calcium and phosphorus in theileriosis affected buffaloes were correlated to gastrointestinal dysfunction and renal damage²¹. Similarly, the decreased levels of calcium and phosphorus in theileriosis positive goats of present investigation can be atributed to marked hepatic, renal and abomasal damage which was evident through gross and histopathological observations.

More or less similar gross and histopathological lesions in various organs or systems including abomasum, lymph nodes, spleen etc. of theileriosis positive goats and other animal species have been recorded frequently ^11,14,22,23. The various atempts²⁴ have been made to study the mechanism of tissue damage in catle experimentally infected or inoculated with Theileria annulata. These earlier atempts²⁴ to elucidate the mechanism of tissue damage in theileriosis demonstrated that, the rapidly proliferating schizont infected mononuclear cells disseminates through the lymphoid tissues from the prescapular lymph node to distant lymph nodes and to the spleen and thymus. The parasitized mononuclear cells also spread rapidly into non-lymphoid organs e.g., liver, kidneys, lungs, abomasum, adrenal glands, pituitary gland and heart. These rapidly proliferating parasitized mononuclear phagocytes produces cytokines viz. TNF-alpha and IFN-alpha. These cytokines disrupt the physiological integrity of the host, can also harm host by disrupting the regulation of the immune and endocrine systems. Furthermore, they stated that, these cytokines produced by parasitized mononuclear cells plays a major role in the development of clinical disease and tissue damage in theileriosis. The pathogenesis of gross and histopathological lesions observed in theileriosis affected goats of present study can be correlated with the mechanism reported by these earlier workers.

In conclusion, our study documented overall prevalence of 38.32% of theileriosis in goat population in and around of Udgir city of Maharashtra state. The diagnosis of theileriosis in goats can be made from blood and lymph node aspiration smear examination in conjunction with characteristic clinical signs, hemato-biochemical, post-mortem and histopathological changes. However, further molecular studies are needed to find out the prevalence of various Theileria spp. responsible for causation of disease in goat population.

Non-significant

Highly significant (P<0.01)

Significant (P<0.05)

Highly significant (P<0.01)

References