Successful treatment of Trypanosoma infection in a wild tiger: A case report

Introduction

Trypanosomiasis commonly known as surra was classified as an OIE notifiable disease in 2009. Natural infections of Trypanosoma have been reported from 48 countries, including 20 in Asia including India; 27 countries have confirmed its presence at least once (Aregawi et al., 2019) [1] . Trypanosomosis is an important blood parasitic infection of both domestic and wild animals and humans (Wiikowsky, 2022) [27] and is most common in tropical and subtropical countries and is endemic in the Indian subcontinent (Shekhar et al., 2024) [22] . The genus Trypanosoma is an extracellular blood parasite and is pathogenic to more than 30 wild animal species (OIE 2005) [14] . In Asia, numerous outbreaks linked to high morbidity and mortality have been recorded in wild animals. Clinical cases and fatalities due to surra have also been observed in endangered species, including tigers i.e. Panthera tigris (More et al., 2017) [11] . Recently, it has emerged in non-endemic regions, infecting novel host species and prompting concerns about its zoonotic potential, as evidenced by occasional human infections (Joshi et al., 2005 and Powar et al., 2006) [8,17] . It is identified as disease likely to spread due to climate change but scientific data are lacking in wildlife trypanosomiasis. [28,19,23,16] . Similar mortalities in zoos in Lahore (Pakistan) and Dhaka (Bangladesh) have also been reported. Despite its wide distribution, current information on the prevalence and economic impact of feline trypanosomosis in India remains limited.

In wild animals, Trypanosoma may be transmitted in four ways: i) mechanical transmission by the bite of a bloodsucking insect either from a local reservoir host (pigs, cattle, sheep, goat) or from an exotic animal species in the zoo; ii) iatrogenic transmission through the infected bloodcontaminated needles and surgical instruments (Parija & Bhattacharya 2001) [16] ; iii) and in carnivores by ingestion of freshly cut meat from infected dead animals (Raina et al., 1985 and Mandal et al., 2017) [18,10] . iv) vampire bats which are also reported to have a unique ability to act as vector and host of this disease (Gingrich et al., 1983). The oral transmission through ingestion of meat and blood of animals infected with Trypanosoma has been considered as an important mode of transmission and has been well described (Baker, 1968; Raina et al., 1985 and Mandal et al., 2017) [2,18,10] . Leeches may also transmit trypanosomes, a factor worth examining, particularly in relation to the buffalo leech (Hirudinaria manillensis) in Asia (Desquesnes et al., 2013) [3] . In the present case, the mode of transmission could not be traced. The parasite is mechanically transmitted by haematophagous flies (Veer et al., 2002) [26] of the genera Tabanus, Stomoxys (Parashar et al., 2006) [15] , Haematopota, Liperosia and Chrysops (OIE 2005) [14] . The success of transmission depends on the parasite's ability to survive in the oral cavity of the vector. Trypanosoma does not survive in the proboscis of flies for more than 10-15 minutes, and must therefore be transmitted to an uninfected host during the same feeding period. This makes transmission more likely in conditions where animals are kept in close proximity, such as in crowded cages. In contrast, tigers are solitary by nature, which offers them a degree of natural protection against such vector-borne transmission. Transmission of infection to carnivorous animals is comparatively easier in comparison to other animals as it may get infected either by biting flies or by ingesting infected flesh (Raina et al., 1985) [18] . Though it is a significant parasitic disease affecting wild animals globally, literature specific to wildlife trypanosomosis remains scarce. The present communication is a case of trypanosomiasis in a tiger at Maharaja Martand Singh Judeo White Tiger Safari and Zoo, Mukundpur, Maihar (Madhya Pradesh) during October 2024.

Case history, Clinical Observation and diagnosis

The case is of a rescued male Royal Bengal tiger (Panthera tigris) named Raja at Maharaja Martand Singh Judeo White Tiger Safarai and Zoo, Mukundpur, Maihar district, Madhya Pradesh, India. The tiger was approximately eight years and weighing about 180 kg. History revealed that the tiger was found anorectic, inactive, and lethargic was found lying dull, depressed in the open area. Immediately the animal was shifted to a squeeze cage and restrained for physical examination. Clinical examination revealed increased rectal temperature (105.7 0 F), tachypnoea (68-75 breaths per min.), increased pulse rate (130 beats per minute as measured from tail vein) and dry muzzle. The animal was ailing in pain as evident from his restless behavior and loss of normal aggressive behavior. Blood samples were collected via venipuncture of the coccygeal vein before treatment. Blood smears were prepared immediately, air dried and fixed in methanol for further staining. Remaining blood was used for hematology and serum biochemistry, the results of which are detailed in Table No. 1 and 2. The blood smears were stained with Geimsa's stain (Schalm, et al., 1975) [20] and examined under microscope which revealed the presence of unicellular, extracellular organism with typical morphology consistent with trypomastigotes, confirming diagnosis of trypanosomiasis. The species of the trypanosome could not be determined because the immunodiagnostic test was not conducted.

Treatment and Discussion

The tiger was treated with Injection deminazine aceturate at the dose rate of @ 3.5 mg per kg b.wt IM. along with symptomatic and supportive therapy including injection meloxicam @ 0.3 mg per kg b.wt. IM for 2 days, injection multi-vitamin-8 ml IV for 3 days, injection pantoprazole-80 mg (total dose) IV along with 0.9% NS (3 litres) for 3 days. The temperature started receding gradually in 2 hours after the treatment. The animal was offered mutton soup that night. Next evening it was offered 3 kg buffon which the animal consumed immediately. Injection deminazine aceturate was repeated after 48 hours @ 3.5 mg per kg b.wt IM. Injection Oxytetracycline @ 15 mg/Kg b.wt was also given intravenously for 3 days to give complete cover against the secondary bacterial infection. Blood smears of 4 th days and 7 th day were negative for parasites. The changes in haemato-biochemical parameters values on day 1 and day 7 th are detailed in Table 01 and 02. The supportive therapy with multivitamins and haematinics was continued for 10 days. Trypanosoma evansi is an important protozoan parasite of tigers. Major outbreaks as well as sporadic cases of trypanosomiasis have been reported in tigers in captivity in India (Singh et [23,16,19,21] . In the present case the tiger exhibited signs of fever, anemia, tachypnea, increased pulse rate, lethargy, restlessness and depression. Several other workers also reported major clinical findings which include fever, anemia, weight loss, edema, lymphadenomegaly, uncoordinated movements (gait) and sudden death (Muhammad et al., 2007; Khan et al., 2015 and Shalini et al., 2025) [12,9,21] . Wild carnivores infected with trypanosomes may display typical signs similar to those exhibited by domestic species, or may succumb without showing any signs. In the present case the haemato-biochemical parameter reports indicated anaemia, hypoglycaemia and increased, liver enzyme values, creatinine and BUN values which showed good improvement and returned to normal by 7 th day. Decreased PCV, TEC, blood glucose and increased ALT, AST, serum creatinine, BUN were also reported by Gupta et al., (2009) [6] , Zubaidah et al., 2021 [29] ; Habila et al., 2012 [7] and Garba and Mayaki, 2018 [4] .

Diminazine aceturate @ 3.5 mg/kg b.wt was given IM and then repeated after 48 hrs (Khan et al., 2015) [9] gave good result and the tiger started consuming 70-80% food offered to it by 3 rd day. Khan et al., 2015 [9] , Zubaidah et al., 2021 [29] and Muraleedharan (2015) [13] all reported diminazine aceturate to be effective in treating trypanosome cases in tigers.

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