South Asia is home to roughly 4,367 Bengal tigers: 3,682 in\u00a0India, 429 in\u00a0Nepal, 131 in\u00a0Bhutan\u00a0and 125 in\u00a0Bangladesh, according to the latest estimates.<\/p>\n
The IUCN\u00a0lists the Bengal tiger as an endangered species, although it is classified as\u00a0critically endangered\u00a0in Bangladesh.<\/p>\n
Bangladeshi researchers, analyzing fecal samples collected from wildlife across the Sundarbans mangrove forest,\u00a0detected\u00a0the highest parasite infection rate in Bengal tigers. A study published by the Bangladesh Forest Department in July makes recommendations to address the issue.<\/p>\n
Sultan Ahmed, a professor in the Department of Microbiology and Immunology at Sylhet Agricultural University and one of the authors of the study, told Mongabay, \u201cThe most important recommendation is to keep the mangrove forest away from human interference.\u201d<\/p>\n
Assigned by the Forest Department, the researchers collected fecal samples in two phases in 2024 and 2025.<\/p>\n
According to their analysis, the highest parasite infection rate, 85.3%, was detected in Bengal tigers, followed by 84.9% in rhesus monkeys (Macaca mulatta<\/em>), 73.6% in deer and 66.7% in wild pigs.<\/p>\n In molecular analysis, roundworms (including\u00a0Toxocara cati<\/em>\u00a0and\u00a0Strongyloides spp.<\/em>), hypdatid worms (Echinococcus granulosus<\/em>), liver flukes (Opisthorchis clonorchis<\/em>) and parasitic tapeworms (Spirometra spp.<\/em>) were detected as the predominant parasite species in the wild animals studied.<\/p>\n The study across the Bangladesh part of the Sundarbans found households were, on average, about 450.7 meters (1,479 feet) from the forest, but the median distance was just 100 m (328 ft), indicating that many homes were located close to the forest edge.<\/p>\n It said that the proximity and shared environments between domestic animals and wildlife facilitate the transmission of pathogens across species.<\/p>\n Published in 2025, a separate\u00a0study\u00a0on Bengal tigers and leopards at the Wildlife Research and Training Centre in Gorewada in the Indian state of Maharashtra, detected several parasitic infections, including\u00a0Sarcocystis spp.<\/em>,\u00a0Toxocara cati<\/em>,\u00a0Spirometra spp.<\/em>\u00a0and another form of tapeworm,\u00a0Diphyllobothrium spp.<\/em><\/p>\n This study\u2019s researchers warned that such infections can cause chronic malnutrition, especially under stressful conditions and affect Bengal tigers\u2019 fitness and reproductive success, and, in severe cases, lead to death.<\/p>\n Citing studies in Maharashtra in western India, the researchers suggested that habitat encroachment and the resulting human-wildlife interactions increased the risk of parasite transmission between wild and domestic animals, as free-ranging wildlife was found to be exposed to diverse pathogens in shared environments.<\/p>\n Parag Nigam, Head of the Department of Wildlife Health Management under the Wildlife Institute of India, observes that domestic cattle, buffalo and free-roaming dogs serve as primary reservoirs for\u00a0helminths,\u00a0flukes, and tick-borne pathogens, which spill over into shared pastures and water sources.<\/p>\n Stressing the importance of breaking transmission chains at human-wildlife boundaries and maintaining high natural immunity across wild populations, he told Mongabay, \u201cThe most effective baseline measure is managing the livestock buffer surrounding tiger reserves.\u201d<\/p>\n Another 2025\u00a0study\u00a0on gastrointestinal parasites in wild mammals in Chitwan National Park, Nepal, found that the proximity of wildlife habitats to human settlements in Chitwan intensifies the risk of zoonotic transmissions, particularly from parasites such as\u00a0Strong-yloides spp.<\/em>\u00a0and\u00a0Toxocara spp.<\/em><\/p>\n One of the authors of the study, Babita Maharjan, an assistant professor at Tribhuvan University\u2019s Amrit Campus and a member of the Nepal Zoological Society, told Mongabay. \u201cWildlife-livestock interaction may increase the risk of transmission of infections to tigers directly through consumption of infected livestock and indirectly through shared habitats, water resources, and infected prey populations.\u201d<\/p>\n In 2018, a Bengal tiger in Bhutan was diagnosed with fatal neurocysticercosis, an infection of the central nervous system, caused by\u00a0Taenia solium<\/em>, commonly known as pork tapeworm, marking the first recorded case of this human parasite in a non-domestic cat.<\/p>\n Analyzing the death, a 2021\u00a0study\u00a0said that the mechanism for the parasite exposure in this unusual case was unknown.<\/p>\n However, the study says: \u201cIt is possible that the tiger may have ingested infective\u00a0T. solium<\/em>\u00a0eggs through direct consumption of human fecal or consumption of water or food contaminated with human feces.\u201d<\/p>\n Camera-trap records from Bhutan\u2019s Nature Conservation Division showed that the deceased tiger\u2019s home range extended to the outskirts of hugely populated Thimphu, according to the study.<\/p>\n Wildlife health expert Parag said parasites are a real issue for Bengal tigers, but poaching, forest degradation and shortage of prey are still the main enemies of the animal.<\/p>\n \u201cThat said, you can\u2019t just ignore these parasites either,\u201d he said. \u201cThey act like a slow, quiet drain on a tiger\u2019s health.\u201d<\/p>\n A strong, fully grown, wild tiger can usually handle a basic parasite load without much trouble but if it gets old, injured or can\u2019t find enough food, these intestinal worms and tick-borne blood parasites take a heavy toll, Parag explained.<\/p>\n The parasites weaken the animal further, cause severe anemia and ruin its ability to hunt wild prey. A weak tiger then turns to village cattle because they are easier to catch, which directly triggers human-tiger conflict in the fringe areas.<\/p>\n \u201cThe bigger worry is what happens to the cubs, and smaller, isolated reserves,\u201d Parag said. \u201cRoundworms and flukes can easily kill young cubs before their immune systems even build up, which hits the local tiger population growth hard.<\/p>\n \u201cPlus, in smaller pockets where tigers don\u2019t have enough genetic variety, their immunity takes a hit, making whole groups vulnerable to sudden sickness.\u201d<\/p>\n Zoologist Babita warned that parasitic infections can be a serious health and conservation concern for Bengal tigers, particularly when an animal is immunocompromised, injured, nutritionally stressed or exposed to heavy or multiple infections.<\/p>\n \u201cMultiple infections are often more damaging than single infections, can weaken the immune system, and make an animal more susceptible to additional diseases,\u201d she said.<\/p>\n Sultan, one of the authors of the latest study, suggested an integrated, long-term wildlife disease surveillance program in the Sundarbans to monitor parasitic and other infectious diseases in Bengal tigers and their prey species.<\/p>\n He also advised parasite control in livestock and domestic animals around the mangrove forests and periodic de-worming of forest department staff.<\/p>\n \u201cA Central Wildlife Disease Diagnostic Laboratory should be established,\u201d Sultan said.<\/p>\n Parag said that minimizing parasitic risks in wild tigers requires landscape-level, ecosystem-based strategies rather than direct veterinary interventions.<\/p>\n He recommended that authorities implement routine, non-invasive monitoring by analyzing fecal samples collected during annual, on-site surveys.<\/p>\n Prey population management plays a vital, indirect role in mitigating parasitic threats, Parag added: \u201cWhen wild prey is abundant and easy to hunt, tigers remain in peak physical condition, allowing their immune systems to naturally suppress and tolerate endemic parasite loads.\u201d<\/p>\n To take advantage of prey management, he suggested prioritizing active grassland management and water-body maintenance to sustain optimal densities of wild ungulates and rigorously surveilling them for disease to prevent outbreaks. Maintaining clean flows of water to limit the concentration of aquatic snails and vector larvae is also required, he said.<\/p>\n Educating forest-dependent communities about proper grazing practices, hygiene and de-worming of livestock can also enhance the effectiveness of these measures to mitigate gastrointestinal parasite infections in tigers, Babita said.<\/p>\n She also recommended interdisciplinary collaboration with epidemiologists, ecologists, biologists and medical and veterinary professionals.<\/p>\n Kolangath, S. M., Upadhye, S. V., Pawshe, M. D., Shalini, A. S., Dhoot, V. M., & Bhangale, P. K. (2025). Parasitic profiling of tigers and leopards of Maharashtra.\u00a0International Journal of Veterinary Sciences and Animal Husbandry, 10<\/em>(3), 42\u201346. doi:10.22271\/veterinary.2025.v10.i3a.2107<\/a><\/p>\n Maharjan, B., Jain, P., & Koju, N. P. (2025). Zoonotic risks and conservation challenges: Gastrointestinal parasites in wild mammals of Chitwan National Park, Nepal.\u00a0International Journal for Parasitology: Parasites and Wildlife, 26<\/em>, 101041. doi:10.1016\/j.ijppaw.2025.101041<\/a><\/p>\n Phuentshok, Y., Choden, K., Alvarez Rojas, C. A., Deplazes, P., Wangdi, S., Gyeltshen, \u2026 Gurung, R. B. (2021). Cerebral cysticercosis in a wild Bengal tiger (Panthera tigris tigris) in Bhutan: A first report in non-domestic felids.\u00a0International Journal for Parasitology: Parasites and Wildlife, 14<\/em>, 150\u2013156. doi:10.1016\/j.ijppaw.2021.02.003<\/a><\/p>\nThe role of human settlements<\/h2>\n
Why parasite infection is concerning<\/h2>\n
Prevention measures<\/h2>\n
Citations:<\/b><\/h2>\n
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