Scientists in Australia have identified a parasite in game deer and feral pigs for the first time.

Researchers at Charles Sturt University discovered the Sarcocystis species of parasite during their work and said it sheds light on a previously unrecognized risk.

Several wild game meat species, including deer and feral pigs are hunted and consumed in Australia. 

Sarcocystis can infect humans in two ways: intestinal sarcocystosis is mostly asymptomatic, although symptoms such as nausea, abdominal discomfort, and self-limited diarrhea that typically resolves within 36 hours can occur. Extraintestinal sarcocystosis is usually asymptomatic, with infection of muscles leading to symptoms including painful muscle swelling, fever, muscle tenderness, weakness, and trouble breathing.

The European Food Safety Authority (EFSA) previously identified Sarcocystis hominis and Sarcocystis suihominis as zoonotic hazards.

Potential health risk
The research team examined the oesophagus, diaphragm, and heart tissue from 90 deer and eight feral pigs in the southeastern regions of the country, searching for visual signs of Sarcocystis cysts. Findings were published in the International Journal of Food Microbiology.

Although no cysts were detected, polymerase chain reaction (PCR) testing and histopathology confirmed the presence of the parasite.

Research was led by Professor in Veterinary Parasitology Shokoofeh Shamsi, who said the findings are concerning as they suggest that infected animals, especially those reared free-range, could pass through meat quality checks undetected.

“This poses a potential food safety risk if the meat is consumed without thorough cooking, which could lead to human infection. Understanding the extent of Sarcocystis infections in game meat is crucial for food safety and public health,” she said.

The study also highlighted potential implications for the Australian pork industry, with the growing trend towards free-range pig husbandry. The possibility of infection spreading between feral and domestic pigs in free-range systems underscores the need for ongoing surveillance and research to determine the prevalence and species of Sarcocystis in game animals, said scientists.

Risk from other parasites
As part of National Science Week, from Aug. 10 to 18, the Food Safety Information Council warned about the risk of parasites, including toxoplasmosis and cryptosporidiosis infections.

Cryptosporidium can be spread by swimming in contaminated water, through contact with an infected person or animal, or by drinking unpasteurized milk. 

Shamsi said research by Food Standards Australia New Zealand (FSANZ) and the Australian National University found there were 15,500 cases of toxoplasmosis in Australia each year. People get infected via cats or through eating raw or rare sheep, pork, or game meat.

Another study in Scotland revealed viable Toxoplasma gondii in two venison products.

A previous analysis of retail meat in Scotland identified a high incidence of Toxoplasma gondii in venison products but the risk to public health could not be assessed as parasite viability was not determined.

In the latest work, published in the journal Food Control, 23 venison products were purchased from farm shops or supermarkets in 2020. Viable Toxoplasma gondii was isolated from two of five positive samples.

“This is the first study to report the presence of viable Toxoplasma gondii in retail venison and highlights the potential risk to public health if this meat is eaten undercooked. Consumers should freeze venison, or cook it thoroughly, before consumption to reduce the risk of foodborne toxoplasmosis,” said researchers.

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