Campylobacteriosis, salmonellosis, cryptosporidiosis: human diseases that often originate in animals

A new analysis by the CDC confirms that many human gastrointestinal infections in the United States have a direct animal origin. These recent data illustrate the significant incidence of foodborne zoonoses, particularly those caused by pathogens such as Campylobacter, Salmonella, and Cryptosporidium.  

A Large-Scale Epidemiological Investigation

Published in the Morbidity and Mortality Weekly Report, this extensive CDC study is based on an analysis of more than 15,000 cases of gastroenteritis reported in 24 U.S. states between 2009 and 2021. The goal was to better understand the animal and environmental origins of human intestinal infections. The results are clear: most of the documented cases are attributable to exposure to food of animal origin or contact with animals. Handling raw meat, contact with ruminants, and caring for pet reptiles are among the most frequently reported factors.  

Campylobacter: A Well-Established Foodborne Zoonosis

Campylobacter jejuni stands out as one of the most widespread pathogens. It is one of the leading causes of bacterial gastroenteritis in industrialized countries. This bacteria is naturally present in the intestines of poultry and cattle, where it generally causes no symptoms. In humans, however, it causes severe diarrhea—sometimes bloody—accompanied by fever and abdominal pain. Meat consumption, contact with livestock, and cross-contamination in kitchens are the main identified modes of transmission. In the most severe cases, neurological complications (Guillain-Barré syndrome) or joint complications (reactive arthritis) may occur, particularly in people who carry the HLA-B27 gene.  

Salmonella and Turtles: An Often-Overlooked Risk

The other cause of these infections is Salmonella spp., well known for its presence in eggs and poultry, but also in pet reptiles. The study highlights the resurgence of cases linked to pet turtles, particularly among children. These animals, even if they appear healthy, intermittently shed the bacteria. Handling them, combined with poor hygiene (failure to wash hands, poorly cleaned water bowls), facilitates transmission. This route of exposure is all the more concerning because it is little known to the general public. Yet the link between reptiles and salmonellosis is well-documented enough that the sale of small turtles is now banned in several U.S. states!  

Cryptosporidium: An Opportunistic Parasite Found in Contact with Ruminants

Finally, the Cryptosporidium parasite is also under scrutiny, particularly in rural areas where contact with calves or contaminated water is common. This pathogenic protozoan can survive for long periods in the environment, especially in moist conditions. It causes acute diarrhea, which can be severe in children, the elderly, or immunocompromised individuals. Human cases are often linked to agricultural activities, visits to educational farms, or the consumption of untreated water in rural areas.  

Antimicrobial Resistance, an Aggravating Factor

Beyond their frequency, these infections pose another challenge: growing antibiotic resistance. Campylobacter, in particular, shows marked resistance to fluoroquinolones and macrolides, two classes widely used in human medicine. This trend is largely due to the widespread veterinary use of antibiotics in intensive farming, which creates selection pressure that poses a danger to public health. In light of this situation, experts recommend enhanced surveillance, stricter regulation of use of antimicrobials in livestock farming, and the implementation of good biosecurity practices.  

Prevention: Simple Steps, Major Impact

While these zoonoses are largely preventable, they continue to circulate on a large scale. Better food safety practices at home—such as cooking meat thoroughly, separating raw and cooked foods, and consistently washing hands after any contact with an animal—can significantly reduce the risk. Raising public awareness—particularly among families with young children and those living in rural areas—remains a priority. In addition, health authorities emphasize the need to educate pet reptile owners and to strengthen controls on the sale of animals that may carry gastrointestinal pathogens.