Reptiles may carry zoonotic diseases that pose risks to humans. Children under 5, the elderly and immunocompromised individuals are particularly at risk.
Bacterial infections (including abscesses) occur in all orders of reptiles and are made more likely by bite wounds, injuries or poor environmental conditions. They manifest as small lumps or swellings under the skin and can contain several species of bacteria.
1. Cloaca Infection
The cloaca is an indentation under the tail of most reptiles. It is where the urine and feces pass through. A cloacal prolapse occurs when tissue from this indentation is protruded into the environment outside of the animal’s body. If this happens, the sooner it is reduced and replaced, the better chance the reptile will survive. A veterinarian will examine the cloaca, feces, and possibly take radiographs of the abdomen to identify a cause for the prolapse.
Bacterial infections occur when a reptile’s immune system is weakened, often by illness or poor environmental conditions. Several antibiotics can be used to treat the infection. However, the success of antibiotic treatment will depend on correcting the conditions that contributed to the bacterial infection in the first place.
2. Prolapsed Organs
Reptiles can be infected with Campylobacter bacteria, which can then be shed and cause human infections. Most cases are mild and go away on their own, but it can be serious for infants and elderly people, those undergoing cancer treatment or those with weakened immune systems.
Proper enclosure conditions, such as a sand-soil mix that holds water and increases humidity, can help prevent this problem.
Prolapsed structures include cloacal tissue, the colon, oviducts and bladder. They’re typically caused by tightness or tenesmus in the excretory area or physical injury. In many cases, a vet has to perform a coeliotomy (removal and reconnecting of the organ) to treat it. Keeping the prolapsed tissue moist is important, as it will die if allowed to dry out.
3. Kidney Stones
Reptiles carry Salmonella bacteria which, if ingested by young children, elderly persons and those with weakened immune systems, can cause severe illness including diarrheal disease. Salmonella is shed in feces and is commonly picked up by handling reptiles.
Bacterial infections occur frequently in reptiles whose immune systems are compromised by poor nutrition, environmental conditions and/or improper husbandry practices. Treatment may be difficult unless the predisposing conditions are corrected.
Internal parasites (worms, protozoa) and bacterial infections are the most common causes of death in reptiles. Signs of a parasitic infection vary by species. Some signs include weight loss, listlessness, lack of appetite, bloating and fluid accumulation in the abdomen, bone deformities and inability to move limbs. Blood tests will identify the type of infection and determine the appropriate drug treatment.
4. Paramyxovirus Infection
Reptiles are susceptible to a variety of viruses including those from the family Paramyxoviridae that cause respiratory disease and neurologic disease. These enveloped viruses contain negative-sense RNA genomes and are similar to influenza viruses.
Reoviruses are the cause of severe and fatal disease in many reptile species presenting as pneumonia or neurological disorders. These viruses are characterized by typical cytopathogenic effect (CPE) and electron microscopy, grow well in iguana and Vero cells, and induce CPE syncytical giant cell formation in lizard lungs [140].
Reoviruses and other arboviruses that occur in crocodilian and alligator species have been shown to have potential as zoonotic agents for human infections resulting in severe and potentially fatal diseases such as measles, mumps and West Nile fever virus. However, the thermoregulatory differences between reptilian and mammalian hosts limit their ability to infect humans.
5. Adenovirus Infections
Reptiles (and amphibians) carry species of the genus Adenovirus, which can cause herpes infections and may be able to infect humans, causing campylobacteriosis. These viruses can be spread by people who have contact with a reptile that has the virus and then coughs or sneezes on someone else, or by touching something that is contaminated with the virus and then touching one’s mouth or nose.
Bacterial diseases affect all orders of reptiles, including gastrointestinal disease, hematologic disorders, and soft tissue lesions. These can be caused by infectious agents, or by opportunistic bacteria that infect malnourished or immunocompromised hosts. Molecular techniques can help identify these infections. Septicemia and death are common, particularly in chelonians and crocodilians. At necropsy, these animals show visceral granulomas. Treatment includes fluid therapy, appropriate antibiotics based on culture and antimicrobial sensitivity testing, and correction of environmental conditions.
6. Metabolic Bone Disorder
Metabolic bone disease (MBD) occurs when there is an improper balance of the vitamins, minerals and nutrients that make up a reptile’s bones. The condition can be caused by a number of factors, including dietary levels of calcium and vitamin D3, too much phosphorous and inadequate exposure to UVB light that hinders the production of cholecalciferol which regulates calcium absorption.
Affected reptiles become weak and withdrawn, are unable to walk or even move, and may develop fractures. They have a general feeling of exhaustion and can be reluctant to eat.
MBD is typically seen in lizards and turtles, but has been reported in other reptiles as well. The condition can often be corrected with dietary improvements, calcium and vitamin D supplementation and increased access to full-spectrum UVB lighting. The hormone calcitonin can also be used to prevent the removal of calcium from bones.
7. Parasites
Reptiles can serve as definitive or paratenic hosts for a variety of parasites that may be zoonotic (of concern to human health). Examples include helminths, pentastomids and protozoa. These parasites are commonly transmitted to humans through direct contact or fecal contamination.
Fungal diseases of the skin are common in reptiles that live in captivity and have suppressed immune systems. Unfavorable environmental temperatures and humidity, handling stress, concurrent disease or malnutrition can predispose a reptile to develop a fungal infection.
Heavy infestations of oxyurid parasites (often called “strongyle worms”) in tortoises can be a significant problem causing anorexia, impaction and general debilitation. Treatment is often successful with anthelmintic drugs.