Crocodiles and crocodile products are in use for medical purpose in many countries across the Indian ocean. Stories about this animal were gathered and written by students. They are all part of a pedagogical project, funded by the National University of Singapore and the Université de Paris. The Bestiary site is a work-in-progress and a participatory educational tool, representing animals whose products or body parts are used to promote health and healing.

The Crocodylus siamensis

A story by Leong Ze Hao

The Siamese Crocodile (Crocodylus siamensis; siamensis – ‘belonging to Siam’) is a moderately-sized (rarely exceeding 3m in length) species of crocodile native to freshwater habitats in parts of Southeast Asia such as Indonesia, Laos, Cambodia, Vietnam and Thailand. It is currently categorized as ‘critically endangered’ on the IUCN Red list and estimates suggest that only 500-1000 mature individuals remain in the wild (Bezuijen et al., 2012). The species is recognized by a prominent bony crest behind each eye, and is known to have a mild temperament compared to the other crocodilians. Attacks on humans by this species is extremely rare (Cox, 1998).

Crocodile (Sundarban, West Bengal, India, 2012) © Leo Jalais

Prominence in Thai culture

Peoples’ perception of crocodiles in Thailand, not unlike that of other reptiles in many cultures across the world, has been mediated by our innate fear (possibly an evolved behaviour for us to avoid dangerous animals). The siamese crocodile, despite its non-aggressive nature, has taken up mostly antagonistic roles in Thai cultural depictions. The most famous of them is a folktale ‘Krai thong’ (ไกรทอง) which details a shapeshifting, man-eating crocodile lord named ‘Chalawan’ (ชาละวัน) falling in love with a rich man’s daughter, eventually abducting her to his cave, only to get slayed by the main protagonist of the story, the crocodile hunter krai thong.

I did not enjoy this story as much as the other children because I grew up watching Steve Irwin’s ‘The Crocodile Hunter’ and became an avid admirer of the Crocodiles. Personal feelings aside, a story like Krai thong not only highlights Thai perceptions of crocodiles as vile and evil creatures, but also illustrates the belief that these animals were not unlike humans at all. They are imagined to have human-like feelings and are capable of love. The crocodile lord’s ability to shapeshift into a man, his infatuation with a human lady, and the presence of many crocodile wives who hung out with him in his cave (yes, he did have those too) are evidence to this.

The Siamese crocodiles’ medicinal uses

Despite being critically endangered in the wild, the siamese crocodiles are a species that is extensively farmed and exploited across Southeast Asia. While much of it is for the crocodile leather trade, the medicinal properties that the crocodiles have to offer are also of extreme value. 

> Crocodile Oil Burn Ointment

Crocodile oil, extracted from the fatty tissues of crocodiles (mostly from Crocodylus siamesis) is fairly popular in Traditional Chinese Medicine across China and Southeast Asia. It is thought to be able to cure illnesses and skin conditions (Venter 1985). Crocodile Oil Burn Ointment (COBO) is one of the products. Originally developed in China according to a TCM formula, COBO is synthesized from natural minerals, crocodile oil and Chinese herbal medicines. When tested on lab mice with burn wounds, COBO accelerated healing and regeneration of hair follicles on the surface of the skin. In addition to its burn-healing properties, COBO was also observed to have anti-inflammatory effects on mice with xylene-induced ear inflammations (Venter 1985).

 

> Antibacterial activity of Crocodile Blood Plasma

Crude plasma extracted from the blood of of Crocodylus siamensis has been found to have antibacterial activity against pathogenic bacteria and has novel applications in the field of medicine. Results have shown that up to 80% growth inhibition was achieved with up to six strains of Staphylococcus aureus, Salmonella typhi, Escherichia coli, Vibrio cholerae, Pseudomonas aeruginosa, and Staphylococcus epidermidis, making the plasma of the Siamese crocodile a strong potential candidate for a robust antibiotic (Kommanee et al., 2012).

 

> Antiamoebic and Antitumor Compounds of Crocodiles

Another Asian Crocodile species native to India, Crocodylus palustris, more commonly known as ‘mugger crocodiles’, have also been found to have great potential in the field of medicine. Lab tests have shown that the sera of Crocodylus palustris was able to effectively shut down the viability of amoebae (A. castellanii), and organ lysates were discovered to have considerable cytotoxicity to prostate cancer cells, demonstrating up to 70% host cell deaths (Siddique et al., 2017). While additional research needs to be done in order to realize the potential presented, it does not change the fact that the antiamoebic and antitumor properties of crocodile lysates and sera look incredibly promising.

Crocodile and monkeys (Mukteswar temple, Orissa, India, 2018) © Leo Jalais

The Crocodile Farms and Zoonoses

The crocodiles in the farms are kept in absolutely horrid conditions (IMAGE: Picture taken by the author at the Samutprakarn Crocodile farm a little over a year ago) and most are hybridized with the saltwater crocodile (Crocodylus porosus) to boost growth rate. Despite my abhorrence for the conditions of these farms, I am really awestruck when I see crocodiles surviving in these places. This is no surprise, given that their extreme hardiness has enabled them to survive in poor conditions and outlive the dinosaurs. They are truly marvels of evolution!

Crocodiles, like most other reptiles, can be carriers of a host of disease-causing pathogens that are easily transmissible to humans. The discussion of crocodiles and their zoonoses is especially important in the Southeast Asian context, as there is significant contact between humans and crocodilians (particularly C.siamensis and C.porosus) through extensive crocodile farming, consumption of meat and even pet trade. The two zoonoses – echinostomiasis and salmonellosis – are of particular importance in Southeast Asia. 

 

> Echinostomiasis

Echinostomiasis is a food-borne disease caused by Echinostoma, a genus of parasitic flatworms that infect the gastrointestinal tract. Symptoms of echinostomiasis include abdominal pain, severe diarrhoea and anorexia, and is transmitted through the consumption of infected undercooked meats (Graczyk and Fried, 1998). In parts of Southeast Asia such as Thailand, Laos, Cambodia and Vietnam where the consumption of exotic meat is common, crocodile meat more often than not would also be on the menu. This increases humans’ susceptibility to contracting the disease, making it a zoonosis worth considering in the context of crocodiles in Southeast Asia.

 

> Salmonellosis

Salmonellosis, on the other hand, is caused by the gram-negative bacteria Salmonella. It is commonly spread through direct or indirect contact with reptiles, amphibians or their fecal matter. Like echinostomiasis, salmonellosis can also be caused by the consumption of undercooked meat. It affects the gastrointestinal tract and (in some cases) the blood stream, presenting symptoms not unlike echinostomiasis: abdominal pain, diarrhoea and fever. Unsurprisingly, the many crocodile farms rearing Crocodylus siamensis in Southeast Asia could potentially be major vectors for salmonellosis, as the animals’ caretakers are constantly in contact with the animals and the unsanitary habitats in which they live.

 

Crocodilian Zoonoses

Table: List of Crocodile-carried zoonoses

 

Zoonosis

Geographic Origin of Reports

Main Clinical Signs

Trichinosis

Worldwide

Fever, myalgia, gastrointestinal symptoms

Anisakiasis

Worldwide

Eosinophilic granulomas

Eustrongylidosis

Worldwide

No specific symptoms recorded so far

Echinostomiasis

Asia

Catarrhal inflammation

Peripheral eosinophilia

 

References
Mendoza-Roldan, J. A., Modry, D., & Otranto, D. (2020), “Zoonotic parasites of reptiles: A crawling threat”, Trends in Parasitology, 36 (8), 677-687.
Graczyk, T., & Fried, B. (1998). “Echinostomiasis: a common but forgotten food-borne disease.”, The American Journal of Tropical Medicine and Hygiene, 58 (4), 501-504.
Salmonella infection from frogs and lizards. (August, 2011). Health. (Retrieved October 12, 2021) 
Li, H., Deng, Y., Zhang, Z., Fu, Q., Zheng, Y., Cao, X., Nie, J., Fu, L., Chen, L., Xiong, Y., Shen, D., & Chen, Q. (2017;2016;). “Evaluation of effectiveness in a novel wound healing ointment-crocodile oil burn ointment”. African Journal of Traditional, Complementary, and Alternative Medicines, 14(1), 62-72. 
Kommanee, J., Preecharram, S., Daduang, S., Temsiripong, Y., Dhiravisit, A., Yamada, Y., & Thammasirirak, S. (2012). Antibacterial activity of plasma from crocodile (crocodylus siamensis) against pathogenic bacteria. Annals of Clinical Microbiology and Antimicrobials, 11(1), 22-22. 
Siddiqui, R., Jeyamogan, S., Ali, S. M., Abbas, F., Sagathevan, K. A., & Khan, N. A. (2017). Crocodiles and alligators: Antiamoebic and antitumor compounds of crocodiles. Experimental Parasitology, 183, 194-200. 
Bezuijen, M., Simpson, B., Behler, N., Daltry, J. & Tempsiripong, Y. 2012. Crocodylus siamensis. The IUCN Red List of Threatened Species 2012: e.T5671A3048087. 
Cox, M. J. (1998). A photographic guide to snakes and other reptiles of peninsular Malaysia, Singapore and Thailand. Ralph Curtis Books.
Bale, R (2020, March 6). Why are we afraid of snakes? National Geographic. 
Venter, T. (1985). Characterisation, toxicology and clinical effects of crocodile oil in skin products (865165937) [Doctoral dissertation, North-west University].