Snakes, bearded dragons, geckos, turtles, and other reptiles have become popular pets in Germany. Data from Germany’s pet industry associations indicate that the number of terrariums in German households has remained relatively stable since 2019, at about 1.2-1.3 million. The figure refers to terrariums, not the number of animals kept in them.

Reptiles can carry microorganisms that are potentially pathogenic to humans without showing signs of illness. In humans, these pathogens can cause illnesses ranging from self-limiting gastroenteritis to chronic skin and soft tissue infections, as well as rare invasive bacterial and parasitic infections. Among the pathogens transmitted from reptiles to humans, Salmonella is by far the most clinically important.

Salmonella Infection

Therefore, in cases of salmonellosis with no identifiable food source, household reptiles should always be considered. Reptiles are a known source of Salmonella and can carry and shed bacteria without showing clinical signs of infection. However, the prevalence of Salmonella varies substantially according to reptile species, population, and housing conditions. An older study from Germany and Austria detected Salmonella in more than 50% of the reptiles examined, although this figure cannot be generalized to all reptiles. A 2025 large meta-analysis estimated a pooled prevalence of approximately 30% across different reptile groups, with substantial differences among snakes, lizards, and turtles.

Transmission occurs through the oral fecal route, including through contaminated hands, terrariums, water bowls, equipment, or water from aquaterrariums. Direct contact with animals is not required. Salmonella can also spread through the environment or through individuals who have previously had contact with a reptile or habitat. Therefore, indirect exposure can be particularly relevant for young children.

After an incubation period typically ranging from approximately 6 hours to 6 days, patients generally develop acute gastroenteritis with diarrhea, fever, and abdominal cramps. Nausea and vomiting may also occur. Diarrhea is usually watery but can contain blood or mucus. In most immunocompetent patients, the illness resolves spontaneously within several days.

Young children, older adults, and individuals with weakened immune systems are at a particularly high risk for severe disease. Invasive infections can spread from the intestine into the bloodstream and then to other organs, potentially causing bacteremia, sepsis, or focal extraintestinal infections.

Diagnosis is made by microbiological detection of the pathogen in stool samples. Molecular methods can be used in addition to traditional culture methods. Blood cultures are also indicated when invasive infection or sepsis is suspected. The treatment of uncomplicated gastroenteritis initially focuses on replacing fluid and electrolyte losses and providing symptomatic care.

Routine antibiotic therapy is generally unnecessary for uncomplicated nontyphoidal Salmonella gastroenteritis. Antibiotics can prolong pathogen shedding and should primarily be reserved for patients with severe or invasive disease or those at increased risk for an invasive course. Antibiotic selection should be guided by pathogen identification and resistance testing, when possible.

Importantly, a healthy appearing reptile may still carry Salmonella. Health authorities therefore recommend particular precautions in households with children younger than 5 years, adults aged 65 years or older, or individuals with weakened immune systems. The CDC advises households with members of these at-risk groups to choose different types of pets. Consistent handwashing after contact with the animal, its food, or its environment, along with keeping terrarium equipment away from areas where food is prepared, are key preventive measures.

Mycobacterium Infection

While Salmonella primarily causes gastrointestinal illness, other reptile-associated infections can present differently. For example, chronic or unusually slow-healing skin lesions after contact with aquariums, aquaterrariums, or aquatic animals should raise suspicion of Mycobacterium marinum infection.

M marinum is a slow-growing nontuberculous mycobacterium found in aquatic environments that can colonize biofilms in aquaterrariums or aquariums. Human infections typically occur when contaminated water or material enters the skin through small wounds. Injuries sustained while handling aquatic animals can also provide entry points.

A characteristic presentation is a slowly progressive papule or violaceous-red nodule, often on the hands or forearms. Several weeks may have passed between exposure and the appearance of visible skin lesions. Consequently, the infection may initially be mistaken for a routine bacterial wound infection, fungal infection, or noninfectious granulomatous condition.

In some patients, the infection remains confined to the skin and subcutaneous tissues. However, it can spread along the lymphatic vessels and involve tendon sheaths, joints, or bones in deeper infections. In patients with chronic, treatment-resistant skin lesions on the upper extremities, clinicians should specifically ask about work with aquariums or aquaterrariums and contact with aquatic animals.

Diagnosis requires a careful history of exposure and microbiological identification of the pathogen from appropriate tissue or biopsy material. The laboratory should be specifically informed when an M marinum infection is suspected. The bacterium grows preferentially at lower temperatures than many other human pathogenic mycobacteria, typically around 28 °C to 32 °C, and cultures may take several weeks. Histopathologic and molecular tests can supplement diagnostic evaluation.

Treatment depends on the extent and depth of infection. Different antimycobacterial regimens may be used, and both monotherapy and combination therapies have been described. Deeper infections generally require longer and more intensive treatment. Current evidence, therefore, does not support a blanket recommendation for combination therapy in all patients. Surgical debridement may also be required when deeper structures, such as tendon sheaths or joints, are involved.

Edwardsiella Infection

Edwardsiella tarda causes diseases in humans much less often than Salmonella or M marinum. This gram-negative bacterium is primarily associated with aquatic environments and various animal species. Reptiles can carry the pathogen but represent only one of several possible sources of exposure.

In humans, E tarda most often causes gastrointestinal illnesses. Wound and soft tissue infections and invasive diseases have also been reported. In extraintestinal infections, exposure to aquatic environments, animals, or contaminated water may provide important diagnostic clues.

Invasive disease with bacteremia or sepsis warrants particular clinical attention. These infections occur primarily in patients with relevant underlying conditions and are associated with substantial mortality. Chronic liver or hepatobiliary diseases, diabetes, malignancy, and immunosuppression have been described as predisposing factors.

Diagnosis is made through microbiological detection of the pathogen, for example, in stool, wound material, or blood. Because E tarda is relatively uncommon in routine clinical practice, exposure history can help guide diagnosis. In patients with atypical wound infections or invasive diseases after contact with reptiles or aquatic environments, this potential association should at least be considered.

Gastrointestinal infections may be self-limiting. Severe extraintestinal or systemic diseases require targeted antibiotic therapy, preferably guided by susceptibility testing. Extensive soft tissue infections may also require surgical treatment.

Campylobacter Infection

When one thinks of Campylobacter, food exposure, particularly poultry, is often the first consideration. Reptiles can also serve as reservoirs for certain species. Of particular interest is Campylobacter fetus subspecies testudinum, a reptile-associated subspecies identified in snakes, lizards, and turtles.

Human infections are rare. Published cases indicate that the clinical presentation can differ from that of typical, predominantly gastrointestinal, C jejuni infection. In older adults and immunocompromised patients, invasive infections and bacteremia have been described. However, only a small number of human cases were available in the original case series of C fetus subspecies testudinum, so a characteristic clinical syndrome cannot be established from these data.

Diagnosis is made on the basis of microbiological detection of the pathogen using stool or blood samples according to the clinical presentation. Therefore, accurate identification of species or subspecies may require additional diagnostic methods. Therefore, in cases of invasive Campylobacter infection without a typical history of food exposure, clinicians should ask about contact with reptiles.

Pentastomiasis

Reptiles can also be a source of rare parasitic zoonoses, including pentastomiasis, which is caused by pentastomides and known as tongue worms. Various species of these parasites use reptiles, particularly snakes, as their definitive hosts. Human infections are rare and have been reported primarily in the tropical and subtropical regions.

In visceral pentastomiasis, humans can become accidental intermediate hosts after ingesting the infected eggs. The larvae develop after ingestion, reaches various internal organs, and can become encapsulated. However, the epidemiology and precise route of transmission vary among pentastomia species; therefore, human pentastomiasis cannot always be attributed to the same exposure route.

Many visceral infections remain asymptomatic and are discovered incidentally during imaging, surgery, or autopsies. Older or calcified lesions may characteristically appear as multiple curved, ring-shaped, or C-shaped calcifications, particularly in the abdomen. The liver and peritoneum are among the most commonly affected sites, although other organs may also be involved.

Severe infection can cause abdominal symptoms and inflammatory complications depending on the location and extent of the disease. Rare severe cases with organ involvement have been described, but the small number of reported cases means that these should not be present as typical manifestations.

Diagnosis is primarily on the basis of characteristic imaging findings and histopathologic examination of tissue. Molecular methods are particularly useful for precise species identification. Currently, there are no established standard drug therapies. Treatment is often unnecessary when asymptomatic calcifications are discovered incidentally, although surgical treatment may be required for severe symptomatic infections or local complications.

Reptile Bites

Classic zoonoses are not the only cause of concern associated with reptile exposure. Bite injuries can also lead to infections. Scientific evidence on snakebites is much more extensive than that on bites from other reptile species.

The oral flora of snakes is diverse and is influenced by species, diet, environment, and housing conditions. Laboratory studies and clinical reports of infected snakebite wounds have identified various gram-negative and gram-positive bacteria, including Aeromonas, Morganella, Proteus, and Enterococcus, along with other opportunistic pathogens. However, the presence of these bacteria in the oral flora alone cannot establish which organisms are responsible for wound infection.

Clinical findings range from localized inflammation with pain, redness, and swelling to abscesses and severe soft tissue infections. After venomous snake bites, venom-induced edema, tissue damage, and necrosis can make it difficult to distinguish toxic inflammatory changes from bacterial infections. Therefore, swelling or necrosis after a venomous snakebite does not automatically indicate wound infection.

Clinically significant bite wounds should be carefully examined and treated according to the nature of the injury. When wound infection is suspected, microbiological samples should be collected, provided this does not significantly delay treatment, so that antibiotic therapy can be tailored to the pathogen and its resistance profile.

Current evidence does not support routine prophylactic antibiotics after every snakebite. Studies and reviews have not shown convincing benefits from general antibiotic prophylaxis, whereas unnecessary antibiotic use can promote antimicrobial resistance and adverse effects. Antibiotics are indicated when a bacterial infection is clinically suspected or confirmed. Other factors, including severe tissue damage, should also be considered when making treatment decisions. The original blanket recommendation that antibiotics should be used exclusively when signs of infection or necrosis are present, therefore, does not adequately address all reptile bites.

In addition to wound care, tetanus vaccination status should be checked and, if necessary, updated in accordance with the current vaccination recommendations. After a venomous snakebite, the priority is to assess envenomation. The need for antivenom depends on the snake species, clinical findings, and severity of envenomation, and this decision should be made independently of the infectious disease assessment of the wound.

Takeaways

Reptiles can transmit various pathogens to humans. Salmonella is clinically important, particularly for young children, older adults, and immunocompromised patients. However, rare infections caused by M marinum, E tarda, or reptile-associated Campylobacter species may also be relevant.

Therefore, a targeted exposure history is crucial. In patients with unexplained gastroenteritis, chronic skin lesions, atypical wound infections, or invasive bacterial disease, asking about reptile contact, terrarium care, or bite injuries can provide important diagnostic clues.

This story was translated from Medscape’s German edition.