Zoonotic Infections – How Your Pets Can Make You Sick
At MPVH, our goal is to foster animal and human health as well as your bond with your pets. The best way to do this is the diagnoses, treatment, prevention, and control of zoonotic infections.
Zoonoses are diseases that are transmitted from animals to humans. In fact, 75% of emerging infectious diseases are zoonoses! While zoonoses are a huge problem in agriculture (think mad cow disease, H1N1, and avian flu), household pets also transmit diseases to their owners. There are more than 30 diseases that are transmitted from household pets to their owners. Consider this: 50% of dogs have one or more intestinal parasites. Cats, birds, rodents, fish, reptiles, and other exotics also pose risk to their human housemates. While zoonotic infections are considered rare, they are a serious threat. The most common zoonoses are parasite infections followed by fungal infections.
Diseases that you can contract from your household pets include the following:
Salmonellosis is the most widespread bacterial zoonotic infection. 6% of cases are contracted from reptiles, less frequently from other pet species. Salmonella is a normal part of the reptile intestinal flora and owners should assume that all reptiles have salmonella. It is excreted in the feces of an infected animal and transmission occurs from ingestion of feces and also through scratches and bite wounds. Salmonellosis remains infectious in tap water for 90 days and in reptile feces for 30 months, so using sinks and bathtubs for clearing reptile housing and feeding materials increases the risk for human exposure and infection.
Prevention includes good hand washing, wearing gloves when handling reptile housing, and limiting the reptile’s territory in the house. Reptiles also should not be kept in child care centers or around pregnant women. Human symptoms include cramping, diarrhea, and fever within 12 to n72 hours of exposure and can result in meningitis, sepsis, carditis, and death.
Toxoplasmosis is one of the most common zoonotic infections. Cats are the primary carrier, but dogs can expose humans as well due to their tendency to roll in feces and animal remains. The most common way to contract toxoplasmosis is the ingestion of undercooked meat and vegetables, contact with cat feces, and transplacental fetal transmission. Prevention consists of keep cats indoors, wearing gloves while gardening, proper hand washing, and cleaning litter boxes daily (which should be avoided by pregnant women). Toxoplasmosis causes inflammation of the choroids and retina, spontaneous abortion, mental retardation, hydrocephalous, convulsions, deafness, blindness, cerebral palsy, encephalitis, and ocular lesions.
Roundworms and Hookworms
Roundworms are carried by cats and dogs and are very common. The eggs can remain infectious for many years in soil. Infection is caused by ingestion of contaminated soil and can also be excreted in the breast milk of dogs, so puppies can be born infected. Prevention includes proper hand washing and regular de-worming of pets. The larvae migrate through the body, particularly to the eyes, liver, lungs, and central nervous system. Symptoms can include eosinophilia (indicative of allergies or parasites), cough, fever, seizures, abdominal pain, malaise, anorexia, weight loss, and rashes as well as rare incidences of death due to pneumonia, myocarditis, and severe CNS involvement. Roundworms can also migrate to the eyes, causing choriorentisis, and uveitis as well as visual disturbances, squinting, eye pain, and retinal scarring.
Hookworms are very common and are carried by dogs and cats. In humans, the larvae penetrate the skin after contact with contaminated soil. Papules form at the site of infection and a creeping, trailing rash occurs as a result of larval migration, which can occur at the rate of several centimeters per day. The condition is highly itchy, particularly at night.
Tapeworms are found in cats and dogs and are contracted by the ingestion of fleas, which makes flea control even more important. Human infection usually occurs in children and symptoms include anal itching, abdominal pain, hives, and eosinophilia. Worm segments can sometimes be observed in stool.
Rabies is a virus spread by dogs and cats infected by wild animals, such a bats. Three out of the four cases of humans resulted in death in 2009. 92% of the 6,690 cases were in wild animals. Of the rabid animals reported to the CDC in 2009, 81 were dogs and 300 were cats. Of all cases reported in domestic animals, 59.4% were cats. The rabies incubation period is 1 to 3 months and can sometimes be as short as 2 weeks or as long as 1 year. After the incubation period, the infection goes through 3 phases: the prodrome, acute neurologic phases, and coma and death. The prodrome consists of headache, nausea, vomiting, and agitation and anxiety. The acute neurologic stage consists of encephalitis or paralysis in humans with symptoms including fever, hallucinations, seizures, over salivating, goose bumps, and priapism. Finally, the patient lapses into a coma followed by death a few days later. After symptom onset, there is no treatment. Prevention consists of proper wound care, vaccination, and rabies immunoglobulin.
This fungal infection can even be transmitted by asymptomatic animals and symptoms include alopecia, itching, and rash. It affects the nearly hairless areas of the skin.
MRSA (Methicillin-Resistant Staphyloccocus aureus)
MRSA can colonize the skin, mucous membranes, urogenital tract, and alimentary tract. Humans can infect their pets, which can then re-infect their owners, resulting in a cycle of re-infection. Proper hand washing and keeping pets from sleeping in the bed are good ways of prevention. Symptoms include skin and soft tissue infection, inflammation of the bone, endocarditis, pneumonia, and sepsis.
Household pets transmit Lyme disease to their owners through ticks. It is most commonly seen in the northeastern and upper central states. Prevention of Lyme disease includes removal of any seen ticks, using appropriate tick prevention, and vaccination against Lyme disease in addition to wearing long sleeves and pants and light-colored clothing (to better identify ticks on clothing). Symptoms (1 to 36 days after exposure) begin with a rash at the site of the tick bit followed by flu-like symptoms (fever, headache, malaise, muscle and joint pain). If untreated, Lyme diseases progresses to arthritis of large joints, encephalopathy, and carditis.
Scabies is caused by a species of mite and is transmitted by dogs to humans and includes itching and rash. Prevention includes proper hygiene.
Giardiasis is the MOST COMMON protozoal infection from all causes in the US and is carried by all mammals. It is contracted by fecal ingestion, swimming, exposure at daycare centers, certain sexual practices, diapers, and travel to places with low hygiene standards. Symptoms include diarrhea, abdominal pain, and fatigue.
Cat Scratch Disease
Cat scratch disease is most commonly transmitted by cats and sometimes dogs, Symptoms include swelling at the site of the skin lesion, lymph node disease, fever, and weight loss.
Also known as Parrot fever, Psittacosis is most commonly found in parrots and is transmitted through inhalation of bird droppings or nasal secretions. Prevention includes proper disinfection and wearing gloves and other protective clothing while cleaning cages. Infected birds display ruffled feathers, lethargy, and anorexia and can be fatal in humans. The incubation period is 1 to 2 weeks and onset of the disease can be gradual or acute, including shaking chills and high fever. Headaches are the most common complaint with development of a dry, hacking cough. Sore throat and cervical adenopathy are often observed while chest pain, pericarditis, and myocarditis are rare. Patients commonly exhibit photophobia and nosebleeds as well as general myalgia and neck stiffness and spasms, which may lead to misdiagnosis of meningitis.
The Companion Animal Parasite Council recommends the following to prevent parasitic infections in pets:
- Putting dogs and cats on year-round treatment with broad-spectrum heartworm anthelmintics (drugs that expel parasites) that have activity against parasites
- Placing dogs and cats on preventive flea and tick products as soon after birth as possible
- Performing annual physical examinations
- Providing pets with cooked food and fresh, potable water
- Annually retesting the heartworm status of dogs and cats
- Conducting fecal examinations at least once or twice per year on adult pets
“Zoonotic Infections: Your Pets Can Make You Sick by Suzanne Albrecht, Freeland Medical Writer in the August 2011 issue of US Pharmacist
“Parasite 101” by Dwight D. Bowman in the February 2008 issue of Veterinary Forum