Dogs and cats are the 2 most common household pets, and there’s no denying the emotional benefits of having your furry best friends living under your roof. However, it is worth noting that they may inadvertently serve as a direct or indirect source of human infections. One of the major problems experienced by pet lovers is those pesky zoonotic diseases, which essentially refers to those medical conditions that are transmissible between animals and humans. The causative organism may be of bacterial, viral, rickettsial, parasitic, and fungal origin. Animal bites with or without infection continue to be a common occurrence and should always be taken seriously, as the mouth flora of animals is comprised of a multitude of potentially harmful pathogens. Ideally, treatment of infected animal bites must include identification of the animal in order to facilitate accurate diagnosis.
Some of the most common zoonotic diseases are:
Hookworm
Dog and cat hookworms are tiny worms that are transmitted faecal-orally to animals, and they are spread primarily through contact with contaminated soil or sand. Dogs and cats may unintentionally contract the parasite from the environment via contaminated faeces or dirt; or run through contaminated soil, then lick their paws and subsequently ingest the almost invisible, microscopic eggs in that fashion.
Pets can also become pick up with hookworms through congenital modes of infection, from the mother’s milk or colostrum. Hookworm infections in pets need to be taken seriously as they can cause anaemia, lethargy, diarrhoea, and weight loss. Severe infestations, particularly in young pets, can be fatal.
Fortunately, since people are not coprophagic, meaning we don’t consume faecal matter, that’s not how hookworm infections are commonly acquired. People become infected with hookworm eggs or larvae while walking barefoot, kneeling, or sitting on ground contaminated with infected animal poop.
Hookworm larvae have the ability to penetrate human skin, so that is the typical route of infection. The larvae enter the top layer of the skin and cause an itchy rash that may be accompanied by a red squiggly line that will appear subcutaneously where the larvae have migrated.
People who garden without gloves and handle contaminated soil will notice a rash on their hands if they’ve been infected.
Symptoms usually resolve without medical treatment in 4-6 weeks.
To prevent a hookworm infestation, it’s important to get rid of any potentially infective faeces from wild or stray animals around your property that might tempt your dog or a barefoot two-legged member of your family. It’s also a good idea to keep your pet away from the poop of other animals while you’re walking or hiking outdoors.
Ringworm
Ringworm is a condition caused by a fungus that can infect skin, hair, and nails of both people and animals. Ringworm is transmissible between animals and humans through direct contact with the skin or hair of an infected animal. Typical signs of ringworm infection in cats and dogs is patches of hair loss on the body, where the skin may appear scaly or crusty; although some pets have been proven to be asymptomatic carriers. The young and immunocompromised animals are most commonly at risk.
Ringworm infections in humans can appear basically on any area of the body. The area will appear red, scaly, dry and cracked, where a ring-shaped rash may occur. It can get quite itchy. On hairy areas like the scalp or beard the infection will be characterised by patches of hair loss. Infected nails become discoloured and thick and may even get brittle and very dry.
Roundworm
Toxocara roundworms are large, and spaghetti-like in appearance; and they cause a parasitic disease known as toxocariasis
Pets and humans alike can become infected by swallowing roundworm eggs from infected faeces in the environment. Animals can also acquire the infection while nursing through their mother’s milk or through the placents while in utero. Infected puppies and kittens usually do not seem very sick. Those that do may have mild diarrhoea, dehydration, rough coat, and a pot-bellied appearance.
Roundworm infections in people are most commonly transmitted through ingestion of contaminated soil. For example, if you pull vegetables from your garden and don’t wash them thoroughly, you could ingest soil that is contaminated with roundworm eggs.
In people, children are most often affected with roundworm. They are known to migrate through the eyes of small children. This is because humans are not the perfect host for roundworms, so they will to travel through the body and create problems like organ inflammation. Ocular larva migrations happens when the larvae invade the retina (tissue in the eye) and cause inflammation, scarring, and possibly blindness. Visceral larva migrations occurs when the larvae invade parts of the body, such as the liver, lung, or central nervous system.
So for obvious reasons, it’s very important that puppies and kittens be dewormed before they are introduced to young children in order to minimise potential for exposure.
Toxoplasmosis
Toxoplasmosis is a zoonotic parasitic disease that can spread to people and animals through contaminated soil, water, or meat, and from contact with stool from an infected cat. Cats are the main source of infection to other animals as they tend to spend more time outdoors, hunting small prey. This is how they ingest toxoplasmosis-positive raw meat from infected rabbits or rodents. Cats are almost always asymptomatic carriers.
Most healthy people who become infected with Toxoplasma show no signs or symptoms. However, pregnant women and people who are immune suppressed may be at risk for serious health complications than a person with a healthy immune system. Children are also at higher risk.
It is for this reason that doctors will recommend pregnant women do not handle the cat’s litter box. The toxoplasmosis is shed in the kitty’s stools and will most likely serve as the source of infection to the human. Gloves may be used by non-pregnant family members.
Another potential source of toxoplasmosis is raw meat but if it is kept in the freezer for about 3 days the toxoplasmosis in the tissues will get destroyed.
Lyme disease
Lyme disease is a vector-borne illness that is spread by Ixodes ticks, also known as the deer tick or black-legged tick.
Acute Lyme disease causes fever and lethargy. People also tend to get rashes, and dogs tend to develop temporary lameness along with the other symptoms.
In a chronic Lyme infection, dogs, people and also cats (though less likely) can develop polyarthritis, which is an immune-mediated degenerative disease that can lead to kidney complications if left untreated.