Pets provide well documented mental and physical benefits to people. There are many studies that show pets can buffer acute stress as well as diminish their perception of stress. People with pets have been shown to have significantly lower heart rate and blood pressure (both systolic and diastolic) relative to non owners. Pets provide social support and have been proven to benefit all groups of people from healthy adults to children, the elderly, the blind and people with other disabilities, children with special needs, prisoners as well as people with chronic illness and those who are immune-compromised.
The majority of pets do not appear to pose any greater risk to an immune-compromised patient than would interaction with other people or the environment. It may be more detrimental to the well being of the immune-compromised patient to lose a beloved pet than to potentially risk acquiring a zoonotic infection3. These benefits have been actively studied, researched and published in scientific (peer reviewed) journals.
However, these benefits must be balanced with the potential risks of disease communicable from pets, particularly dogs and cats, to people (zoonotic disease). Fortunately these are in fact few and can be easily avoided by good pet care practices and good personal hygiene e.g. washing hands before eating.
Since Toxoplasma has been much talked about, this disease will be explained in detail. There are two types of animals that harbour this parasite – cats and farm animals. The cat is the primary host in whom the toxoplasma organism is able to sexually reproduce and produce eggs (oocytes). Most cats are infected early in their lives (4 – 6 week kittens). They will then shed eggs in their faeces 1-2 weeks after infection. These eggs must then mature for 2 to 5 days before they become infective to humans. After this period cats rarely shed eggs again during their lifetime and thus do not transmit infection. In addition cats are extremely finicky and clean animals. They constantly clean and groom, so unless very sick will never have faecal contamination on their coats.
It has been researched and scientifically proven that there is no correlation between cat ownership and toxoplasma infection in people. In fact there has never been a reported (published) case of a person getting toxoplasma from their pet. Toxoplasma is extremely rare in dogs.
Toxoplasma is transmitted to humans primarily from undercooked meat (pork, lamb specially) containing toxoplasma cysts (asexual form). These farm animals are intermediate hosts and carry cysts in their muscle tissue. It can also be transmitted through raw vegetables, salads or fruits which have not been washed and contaminated drinking water (un-boiled). Some of the highly publicized infections shown in AIDS patients such as toxoplasmosis are due to re- activation of previous infection acquired from meat and do not relate to current pet exposure.
Other diseases from dogs and cats are briefly listed below.
Rabies – from bites and saliva of infected dog or cat: Can be completely controlled by regular vaccination.
Leptospirosis – dog (also rat and some farm animals), through urine contamination of food or drinking water: Can be controlled in dog by vaccination and adequate rat control in households and kennels. Prevent contact with potentially infected urine.
Round worm, hook worm, tape worm – dog and cat: By faecal contamination of food and water or from direct faecal oral route (contaminated hands). Can be prevented by regular de-worming of pets and hand washing before eating.
Bartonaellosis – cats; cat scratch disease: This is probably the most important emerging disease that may be transmitted through bites and scratches from cats. It is transmitted to the cat through fleas. The best method to prevent this disease is effective and regular flea treatment for cats and prevention of cat flea; also by avoiding cat bites and scratches.
Dermatophytosis (fungal skin disease) - cat and dog (Microsporum canis – ‘ring worm’ and Trichophyton mantagrophytes):To prevent this, good grooming and skin care of pets with prompt treatment when infected is very important.
Mange – cat and dog. It is a common misconception that mange is contagious to humans. There are two types. The commonly seen one on stray dogs in Sri Lanka is Demodectic mange (Demodex canis) and is absolutely NOT transmitted to humans, or even other dogs and cats. Recent studies indicate that Sarcoptic mange (Sarcoptes scabiei) was probably not a zoonotic condition.
As can be clearly seen, most zoonotic diseases from pet animals can be easily prevented by regular vaccination and good hygienic practices. Most diseases communicable from pets are transmitted to people indirectly by faecal and urinary contamination of food (uncooked) and drinking water (un- boiled). There are just two exceptions, Rabies and Bartonellosis, which are transmitted through bites and scratches.
Veterinarians and other professionals, including medical practitioners could play a vital role in the education of the public….. these educators must be aware of the changing trends in the transmission of zoonotic parasites. Indeed veterinarians and medical practitioners need to work in collaboration to ensure the best outcome for their animal and human patients respectively. It is irresponsible to create unfounded panic in people with regard to important health issues such as zoonotic disease.
(The writer is Education Officer, Society of Companion Animal Practitioners and Director, Pet Vet Clinic and Trustee, Blue Paw Trust)