Zoonotic diseases are diseases which can be transmitted from animals to humans, which includes domestic cats. Toxoplasmosis and cat scratch fever are the most well known feline zoonotic diseases, but there are more. In this article, we will look at diseases which cats can potentially spread to humans and ways to reduce transmission of zoonotic diseases.
It must be said that while there are risks, transmission of most infections from cats to humans is still rare, and we can reduce the risks significantly by taking proper precautions, which will be outlined at the end of the article. Too often cats are blamed for the spread of disease to humans when compared to other sources, rank pretty low on the list of risk factors for most diseases.
Immunocompromised people, young children, the elderly are most at risk and pregnant women who have had no prior exposure to toxoplasmosis.
At a glance:
Toxoplasmosis is an infection caused by the intracellular parasite ‘Toxoplasma gondii’. It infects multiple warm-blooded animals including humans, livestock, and birds (all of whom act as intermediate hosts). Cats are the only definitive hosts to T. gondii, which means that the parasite is only able to sexually reproduce in felines (both wild and domesticated).
The parasite alters the brain chemistry of its host by forming cysts in the amygdala, which can lead to changes in behaviour, such as risk-taking and a decrease in reaction times. Infected rodents lose their innate fear of cats, which makes them more vulnerable to predation.
Most people have heard of toxoplasmosis due to the risks an infection poses to pregnant women. Infection rates vary from 11% in the US and UK to 95% in some populations. The majority of infected people are unaware they have been exposed to the parasite because they remain asymptomatic. If infection occurs during pregnancy it can cause miscarriage or congenital defects which include brain damage, cerebral palsy, epilepsy, blindness and hydrocephalus.
Cats are the definitive hosts, which means that the cat is necessary for Toxoplasma to complete its life cycle. However, while cats get a bad rap due to this disease, raw meat, unpasteurised goat milk, raw vegetables, and contaminated water are the most common sources of infection.
I personally tested negative to toxoplasmosis during my own pregnancy but had a cat who tested positive. I remained negative throughout that pregnancy and a subsequent one by taking proper precautions which included having my partner clean the litter trays, cooking meat thoroughly and washing all fruit and vegetables.
Oocysts are shed in the cat’s feces, and once in the environment, they become infective after 1-5 days. The next host (human, or other animal) becomes infected by ingesting sporulated oocysts on from contaminated water, food or cat feces.
Most infected cats show no symptoms. Kittens, young cats, and cats who are immunosuppressed (for example, those infected with Feline Immunodeficiency Virus or Feline Leukemia Virus) are most likely to display symptoms, which may include:
- Loss of appetite
More severe symptoms will depend on which part of the body is infected but can include inflammation in the eye (retina, iris or cornea), pneumonia, central nervous system disorders such as head pressing and circling, pancreatitis, hepatitis (inflammation of the liver), jaundice, vomiting and diarrhea, enlarged lymph nodes.
As with cats, symptoms are usually rare in immunocompetent and up to 80% of people infected are unaware they have the infection. If symptoms do occur, they may include:
- Localised lymph node tenderness
- Flu-like symptoms such as a sore throat, fever, headache
- Muscle aches
Healthy, non-pregnant individuals and cats usually require no treatment.
If you are pregnant or are immunocompromised due to HIV or medications your caregiver will prescribe a course of antibiotics.
Ringworm (dermatophytosis) is a common fungal infection which affects the skin, fur, and nails of cats. It is caused by a microscopic group of parasitic fungal organisms known as dermatophytes, meaning “plants that live on the skin“.
Ringworm invades the dead, outer layers of the skin, claws, and hair. The name ringworm comes from the ring like, circular lesions which develop on the cat’s skin. The fungus is more common in areas of high humidity and temperatures.
Kittens and senior cats, cats in crowded environments such as catteries and shelters are at greater risk. Persian and Himalayan cats appear to be more predisposed to the disease than other breeds which may suggest a genetic component.
Ringworm is extremely contagious. A cat can become infected with ringworm in the following ways:
- Direct contact: With an infected animal. This may include grooming, rubbing against each other, sleeping together.
- Indirect contact: Clothes, bowls, furniture, and hands which have been in contact with an infected animal.
- Environment, such as contaminated bedding, grooming equipment, cat carriers, carpet, furniture, air vent filters, and soil. Spores attach to the hairs, which are shed into the environment and can remain infective for up to 18 months.
Most healthy adult cats and people have a natural resistance to the fungus.
Symptoms (cats and people):
- Circular patches of rough, scaly skin with a red outline and broken hairs or bald patches.
- Small pustules in the area of hair loss.
- Lesions are the result of an inflammatory response to the fungus and are found most often on the head, pinnae followed by the limbs and tail, however, any part of the body can be affected.
- Lesions may range from small and barely noticeable to severe, affecting large parts of the body. Ringworm may or may not be pruritic (itchy).
- Large areas of hair loss may occur without characteristic rings, crusts or exudate.
- Severe cases of ringworm may lead to folliculitis and/or secondary infection of the skin.
Medicated dips, creams and drugs to kill the fungus. It is also important to decontaminate the home as spores can spread to soft furnishings, walls and carpets. A 1:10 bleach solution is the most effective method.
Salmonellosis is a bacterial infection caused by the Salmonella bacterium. It is a common cause of enteritis (inflammation of the intestines) with associated vomiting and diarrhea. Salmonella can affect a wide range of animals including humans, wild animals, domestic pets, farm animals, birds, fish, reptiles, and amphibians.
There are almost 2,000 serotypes of the genus Salmonella which live in the intestinal tracts of the infected host. Salmonella is rare in cats, however, it is of particular importance because it is a zoonotic disease, which means one that cats can transmit to humans.
Symptoms (cats and people):
Most infected cats will be asymptomatic (subclinical carrier state).
Salmonellosis is rare in cats, they are thought to have a natural immunity to the bacteria. Risk factors which can make a cat more susceptible to salmonellosis include the strain of salmonella (some are more pathogenic than others), cats in high-stress situations and environments such as shelters, immunocompromised cats, general poor health status, hospitalised animals, young and old cats.
Kittens, senior cats, and cats, with weakened immune systems are more likely to be clinically affected than healthy adult cats.
Cats have been found to shed the serotype of salmonella which is pathogenic to humans. However, there are very few (if any) reports of human infection from cats. There is a much, much greater risk of becoming infected via infected food.
When the cat grooms, bacteria in the saliva transfer onto the coat which can contaminate the environment. Take care handling a cat with salmonella as well and decontaminate the environment.
Symptoms of salmonellosis appear after 2 – 4 days of exposure and can include:
- Diarrhea (may or may not contain blood or mucus)
- Poor appetite (anorexia)
- High fever
- Abdominal pain
- Weight loss
- Symptomatic cats will receive fluids to treat dehydration and replace electrolytes.
- Oral antibiotics.
Escherichia coli (E. coli) is a bacteria which usually resides in the gastrointestinal tract of mammals (including cats and humans) without incident. There are hundreds of strains of E. Coli, most of which are harmless, however, some strains are pathogenic, resulting in sickness.
There are typically two modes of transmission to cats:
1) When normal gastrointestinal bacteria find their way to other parts of the body, such as with urinary tract infections.
2) When a cat consumes a pathogenic strain of E. Coli.
People become infected when they come into contact with cat feces infected with E. Coli.
Symptoms (cats and people):
Symptoms of E. Coli vary depending on the location of the infection but may include:
- Diarrhea, which may be blood tinged
- Loss of appetite
Giardia is a protozoal infection of the small intestine. Giardia duodenalis (G. lamblia) can infect a wide range of mammals and is split into several assemblages (subpopulations) with of which has a preferred host.
- A1 – Humans and a wide range of mammals including cats and dogs
- A2 – Humans
- A3 – Hoofed wild animals
- B – Wide range of mammals, including humans and cats
- C – Dogs and other canids
- D – Dogs and other canids
- E – Hoofed animals
- F – Cats
- G – Rodents
One study in Australia found the prevalence of Giardia in healthy cats to be 2%, although those numbers may be up to 12% in crowded conditions such as shelters and catteries. Infection in kittens and young adults are most common as well as cats in over-crowded or stressful environments and immunocompromised cats.
This answer is still not entirely known so it is safe to err on the side of caution and assume transmission of giardiasis from cats to humans is possible.
As you can see from the assemblages, cats can be infected with A1 or F, whereas humans are infected with A1, A2 and B. So it is feasible that if your cat has become infected with A1, transmission is possible. It is unlikely that a cat infected with F could pass it on. Regardless, it is always better to play safe and assume infection is a possibility and make appropriate safeguards when dealing with an infected cat.
- Drinking water: Contaminated water is one of the most common modes of transmission in both cats and people.
- Fur or skin: Contact with infected feces in the environment, such as digging in a litter tray or a garden bed and then licks his coat.
- Food: Consuming food which contains infective cysts. Contamination can occur during preparation from a person who has the cysts on their hands or contaminated equipment.
- Fomites: Contact with contaminated objects which can be transferred to the cat’s coat and later ingested when the cat grooms.
- Direct contact with an infected animal or person.
Symptoms (cats and people):
Most cats are asymptomatic, even so, just like cats with clinical signs, asymptomatic cats may shed cysts in their feces. Clinical occur most often in younger animals from multi-cat households/environments or those with concurrent illness. The parasite has a one to two week incubation period. Symptoms in both cats and people follow a similar path.
- Acute, chronic or intermittent diarrhea. Stools are foul smelling, often yellowish, foamy/frothy and greasy
- Abdominal pain
- Vomiting (occasionally)
Cats: There are a number of medications which may be used to treat clinically affected cats, however, no drugs been approved for treatment of giardia in cats in the USA.
People: Drink plenty of fluids to avoid dehydration. In some cases, antibiotics will be prescribed.
Cryptosporidiosis (or crypto) is the name of a protozoal infection affecting the small intestine and sometimes the respiratory tract of affected hosts. It is caused by single-celled parasites of the genus Cryptosporidium which infects a wide variety of vertebrates including cats, dogs, humans, horses, and livestock.
There are up to 50 sub-species of Cryptosporidium with have their preferred hosts. While cats (and humans) can be infected with sub-species normally found in other animals, infection tends to be less severe. The natural hosts of the sub-species have been included in bold font.
- Cryptosporidium felis – Cats and occasionally humans (rare)
- Cryptosporidium canis – Dogs and occasionally humans (rare)
- Cryptosporidium parvum – Cattle, sheep, goats, cats, dogs, humans
- Cryptosporidium hominis – Humans
- Cryptosporidium meleagridis – Turkeys, parrots and humans
- Cryptosporidium muris – Rodents, cats, occasionally humans (rare)
Infection occurs via the fecal-oral route. Once the oocysts have become infective in the environment they infect their next host in a number of ways.
- Drinking contaminated water. This is usually from untreated water supplies such as lakes, dams etc., but occasionally the water supply can become contaminated.
- Eating contaminated food. This may have occurred during preparation (unwashed hands, contaminated food preparation area), or during slaughter or infected prey.
- Exposure to objects (fomites) which have been contaminated with oocysts such as food bowls, litter trays.
- Ingesting oocysts from the coat during self or mutual grooming.
Healthy adults are often asymptomatic. Kittens under six months and immunocompromised cats are typically symptomatic. Symptoms can vary depending on the sub-species.
The most common symptom of cryptosporidiosis is watery diarrhea, other symptoms may include:
- Anorexia (loss of appetite)
- Abdominal pain
- Low-grade fever
- Dehydration, due to diarrhea
- Weight loss
There are no effective medications to treat cryptosporidiosis in cats. A cat with a healthy immune system will rid themselves of the parasite in time.
Supportive care may be necessary. This may include nutritional support and IV fluids and electrolytes to treat dehydration and anti-diarrheal medications.
In most cases, treatment is not necessary. Drink plenty of fluids to prevent dehydration.
Pasteurellosis is a zoonotic bacterial infection caused by Pasteurella genus. Pasteurella multocida is the most commonly reported organism in this group, and is a common part of normal bacterial flora in animals but can also be pathogenic (disease-causing).
Pasteurella multocida found in the mouths of approximately 75-80% of all cats. Cats with tartar build up and gingival disease have a higher rate of infection than cats with clean teeth.
Pasteurella is the most common disease to spread from cat to cat or cat to human. Infection is most often introduced via bites or scratches.
Because Pasteurella is a common part of the cat’s flora, many cats remain asymptomatic. However, the bacteria is opportunistic and in some cases can infect the gums (stomatitis or periodontal disease), pyothorax, feline acne, bone infection, skin infection, meningitis and bite wound abscesses.
Infection in people from cats is usually the result of a bite or scratch. Symptoms include pain, tenderness, swelling and red skin at the site of the wound. Localised swollen lymph nodes are also common.
In cats, treatment depends on the affected area but will include antibiotics to treat the infection and clean, flush any infection of the skin (including abscesses).
Antibiotics are the treatment of choice for people infected with Pasteurella. If an abscess has developed, it can be lanced, flushed and packed with antiseptic.
Also called black fever, feline leishmaniasis (FeL) is a zoonotic disease caused by an intracellular protozoan parasite of Leishmania. There are two types of leishmaniasis, skin (cutaneous) and visceral. Cutaneous leishmaniasis is most common in cats. Visceral leishmaniasis can affect the liver, kidneys, spleen, eyes and bone marrow.
Leishmaniasis is less common in cats than it is in dogs, it is thought they have a natural resistance to the parasite.
Cats can not spread the parasite directly to people but can be reservoir hosts, which means a cat infected with leishmania can infect a sand fly when it feeds from the cat and go on to infect a human.
The parasite is spread via the bite of an infected sand fly.
- Skin or mucocutaneous lesions (ulcers, crusting, nodular dermatitis, exfoliative), the nose, ears and distal limbs are most commonly affected
- Enlarged lymph nodes
- Hyperkeratosis (excessive scaling and thickening of the skin along with loss of pigmentation)
- Symmetrical areas of hair loss (alopecia)
- Enlarged liver and spleen
- Weight loss
- Kidney failure
The most common drug used to treat leishmaniasis in cats is Allopurinol. This medication interrupts the protein synthesis of Leishmania. This is not a cure, but can keep the parasites in remission. However, the cat will still be infected. Other drugs which may be used include Sodium stibogluconate, Meglumine antimoniate, Fluconazole and Itraconazole.
Surgical removal of skin nodules or pinnectomy (surgical removal of the ear flap) where indicated.
Cats who are severely affected have a poor prognosis and euthanasia is usually the only option.
Visceral leishmaniasis is treated with liposomal amphotericin B.
Small cutaneous lesions may not be treated. Where indicated, medications used to treat cutaneous disease include oral ketoconazole, intravenous pentamidine, or liposomal amphotericin B.
Rabies is a fatal infection of the central nervous system caused by the virus belonging to the Rhabdoviridae family. It is found in nearly all warm-blooded mammals and is of great concern due to it being zoonotic.
The disease is found in all continents of the world except Australia and Antarctica. Although Australia doesn’t have rabies, bats in Australia are known to carry a virus known as Australian bat lyssavirus (ABL), which is a close relative to the rabies virus. There have been no cases of infection in Australian cats although human infection has occurred.
The virus is spread via the bite from an infected animal. Skunks and raccoons are the major sources of infection in the US although most cases of human infection occur as a result of dog bites. Infection is more common in cats than dogs (4 to 1), no doubt due to contact with infected animals when they roam.
During the prodromal (meaning early symptoms) phase, which lasts 1-3 days, the cat may display the following symptoms:
From the prodromal phase, cats may enter the furious phase, which lasts from two to four days. Symptoms include:
- Muscle tremors
- Paralysis of the throat
- Hypersalivation (drooling)
- Paralysis of the rear legs
- Respiratory failure
There is no effective treatment for rabies in cats and euthanasia is necessary. Due to the serious nature of the disease and the risks of transmission to humans, if rabies is suspected submission of the head to the proper authorities is required for rabies testing.
No effective treatment exists for humans either and once symptoms develop, the disease is almost always fatal. If caught early enough, it is possible to administer a series of vaccinations to enable the body to develop specific antibodies to fight off the virus.
Cowpox is a rare viral skin infection caused by the cowpox virus which is a member of the Orthopoxvirus family and a close relative of the now eradicated smallpox virus, which was responsible for the deaths of between 200 – 300 million people in the 20th century.
Cowpox gets its name from the dairymaids who often catch the infection from the udders of cows they milked, however, despite its name, the natural hosts of the virus are in fact rodents. Humans, cats, dogs, horses, rodents, cattle and many other mammals can all become infected with the cowpox virus.
Infection in cats most often occurs as a result of hunting animals infected with the virus. The most common mode of transmission to humans is now via domestic cats. Our beloved felines shouldn’t take all the blame for human infection, though, there was an outbreak of cowpox which occurred between pet rats and humans in France in 2009.
Most cases of cowpox are self-limiting and treatment for cowpox and is generally supportive. This may include:
- Antiseptics to clean lesions and prevent bacterial infection.
- Antibiotics to treat secondary infections.
- Avoid the use of corticosteroids in cats with cowpox as these will make the condition worse.
Cat scratch disease:
Cat scratch disease (CSD) is a zoonotic infection caused by the bacterium Bartonella henselae that can be spread from cats to humans. Infection occurs via bite wounds or scratches from cats or other objects such as thorns and splinters.
Fleas pass Bartonella from one cat to another via flea feces which contains the bacterium. As the flea feeds, feces are deposited onto the cat’s skin which is transferred to the mouth and claws as the cat grooms himself. It is not possible to pass on the disease from human to human.
One study showed approximately 80% of cats had positive antibodies to the bacteria and approximately 50% of cats carry the Bartonella henselae but are asymptomatic.
Cats are the main reservoir of CSD transmission to people, although puncture wounds and scratches from dogs, thorns, splinters and even fish bones have been implicated in a few cases too. Although the bacterium is relatively common in cats, it is quite rare to catch CSD, which indicates that it’s somewhat difficult to catch. Infection occurs in humans via a bite, scratch or puncture.
- Swollen lymph nodes
- Muscle soreness
- Loss of appetite
In most cases, the disease is self-limiting and will resolve itself in time. Thoroughly clean the site of infection with antiseptic.
In severe cases or patients who are immunocompromised, antibiotics will be prescribed. Azithromycin (Zithromax), rifampin, ciprofloxacin, doxycycline, and gentamicin are usually the antibiotics of choice.
Also known as rabbit fever, tularemia is a rare bacterial infection caused by Francisella tularensis. It also has the potential to be used as a biological weapon.
The bacteria can survive for long periods of time in the environment, particularly in warm, moist conditions. It is an intracellular bacteria, predominantly living within the macrophages (a type of white blood cell).
Cats (and humans) can pick up the disease the following ways:
- Eating infected animals, usually rabbits or rodents
- Inhaling the bacteria in contaminated soil or via infected animals
- From the bite of an infected animal
- Drinking contaminated water
- Tick, biting-fly, flea or mosquito bite, intermediate hosts feed on an infected animal, during which time they ingest the bacteria, the next time the insect feeds, the bacteria enter the new host
The incubation period of tularemia is between 1-10 days. The severity of the disease varies according to the route of exposure and the strain. Some infected cats will remain subclinical. The most common first symptom to appear is a sudden onset high fever, other symptoms may include:
- Respiratory infection
- Loss of appetite
In addition, symptoms can vary depending on the type of tularemia your cat has.
- Ulceroglandular tularemia – An inflamed papule develops at the site of exposure, over time this ulcerates, lymph nodes close to the site become swollen and painful.
- Glandular tularemia – Swollen lymph nodes close to the site of inoculation.
- Oculoglandular tularemia – Purulent conjunctivitis, most often in one eye with enlarged lymph nodes.
- Oropharyngeal tularemia – Ulcers on the tonsils, stomatitis (inflamed and sore mouth), swelling of localised lymph nodes, vomiting, and diarrhea.
- Typhoidal tularemia – Symptoms of typhoidal tularemia can be a combination of generalised symptoms such as fever, anorexia, and lethargy.
- Pneumonic (respiratory) tularemia – Coughing, difficulty breathing.
As the disease progresses, septicemia, jaundice, enlarged liver and/or spleen. Possible complications include kidney failure, meningitis, sepsis, hepatitis, disseminated intravascular coagulation, and acute respiratory distress.
Antibiotics for 14 days and during this period your cat must be in isolation to avoid spreading the infection. Medical personnel and pet owners will need to take extra precautions while caring for a cat who has tularemia.
Supportive care such as fluids to treat dehydration and nutritional support.
The plague is an extremely serious zoonotic infection caused by the bacteria Yersinia pestis. This is the bacteria that is believed to have been responsible for the Black Death which wiped out a 30-60% of the population of Europe from 1346.
The natural reservoirs of plague are rats, mice, prairie dogs and squirrels. Cats and dogs are accidental hosts. Y. pestis can be found worldwide but is most prevalent in Africa, Asia, and South America. It is extremely rare in the USA and when it does occur, it is in regional areas of the western states – where it is on the increase in recent years. Dogs are more resistant to the disease than cats, and it is self-limiting.
The plague comes in three clinical forms, symptoms may vary depending on which form your cat has.
- Bubonic: Infection of the lymph nodes. This is the most common and least fatal form.
- Septicemic: Infection of the blood.
- Pneumonic: Infection of the lungs. This is the most severe form of the plague with a 90% mortality rate if left untreated.
Transmission of bubonic and septicemic plague is via the bite of a flea. This is by far the most common mode of transmission. Cats can become infected via the bite of a flea.
Pneumonic plague can be spread by coughing and sneezing.
In some instances, you can also become infected when handling an infected animal who bites or scratches you or from coming into contact with bodily fluids of an infected animal (such as a hunter handling a dead animal). Cats can become infected by hunting/eating infected rodents
The incubation period of the plague is 2-6 days. Symptoms vary depending on the type of plague, but may include:
- Loss of appetite (anorexia).
- Bubonic plague – Swollen, tender lymph nodes, which become abscessed. When cats develop this form of the plague, the lymph nodes in the head and neck are most commonly affected.
- Pneumonic plague – Coughing and sneezing.
Antibiotics, usually streptomycin or gentamicin and supportive care.
Campylobacteriosis is an infection caused by the Campylobacter jejuni bacterium. It is associated with enteritis (inflammation of the small intestine), resulting in diarrhea. Kittens, particularly those under six months of age are most susceptible to infection due to their immature immune systems. The disease is zoonotic which means it can be passed from cat to human and is one of the leading causes of diarrhea in people.
Cats only represent a small proportion of reservoirs of infection to people, undercooked meat is the most common mode of infection in humans. Young children being the most vulnerable to infection.
Infection is spread via the fecal-oral route, which includes:
- Accidental ingestion of contaminated feces or feces particles.
- Raw meat, especially chicken, unpasteurised milk can also be a source of infectioin.
- Contaminated water.
- Fomites (inanimate objects) such as food bowls, litter trays, and bedding.
The incubation period is between 2-5 days. Most cats infected will have no symptoms or display only mild sickness. Common symptoms of campylobacteriosis include the following:
- Watery diarrhea which may contain mucus or blood
- Abdominal pain
- Tenesmus (cramping and rectal pain)
- Loss of appetite
- Vomiting (occasionally)
- Swollen and tender lymph nodes
- Antibiotics to treat the infection.
- Fluids to replace lost fluids and correct dehydration.
- A bland diet to rest the stomach.
- Isolate the affected cats from other pets to reduce transmission.
A infection caused by Mycobacterium tuberculosis which was a huge scourge on mankind until the discovery of antibiotics. Tuberculosis (TB) is rare in cats as they who appear to have a natural immunity to it.
Cats become infected during hunting if they are bitten by an infected animal (usually a rodent) or consuming food or milk which is infected with the bacteria.
Currently, there are only two known cases of tuberculosis which was passed from cat to person. Transmission can occur via respiratory droplets, oral ingestion of the bacteria after contact with infectious lesions, and contamination via cuts in the skin.
Symptoms vary depending on the route of infection.
For cats who have been bitten, lesions appear on the area that was bitten, which is usually around the face and neck. Swollen lymph nodes can also develop.
Cats who have acquired infection via consuming food or milk containing the bacteria, gastrointestinal symptoms are more common including:
- Anorexia (loss of appetite)
- Weight loss
Symptoms of tuberculosis in people includes:
- Coughing (often with blood)
- Chest pain
- Weight loss
Euthanasia is recommended for affected cats treatment can be difficult and there is a high risk of the infection spreading to household members and the wider population.
Long term oral antibiotics are used to treat tuberculosis in people.
Hookworms are small, thin nematodes that are approximately 10 to 20 mm in length and are a common intestinal parasitic worm of dogs but can also infect cats.
Hookworms live in the duodenum, the first part of the small intestine, where they attach themselves to the mucous membrane using teeth-like hooks to feed on the blood. An adult hookworm can consume up to 0.1 ml of blood every day, changing their point of contact every 4-6 hours. A heavy infestation can lead to anemia.
Hookworm infection is possible in people but they don’t develop into adult worms as they do in the cat. Eggs are shed in the feces of the cat (or dog) and develop into larvae in around 2-3 weeks. Infection occurs when a person comes into direct contact with these infective larvae, which are able to penetrate intact skin. They attempt to migrate towards the blood vessels (as they would in the cat or dog) but lack the enzyme necessary to penetrate the deeper layers of the skin and eventually die.
This migration through the skin is known as cutaneous larva migrans (also called ‘creeping eruption’ or ‘ground itch’). Humans are dead-end hosts as larvae aren’t able to penetrate further than the outer layers of skin like they would do in the cat or dog and develop into adult worms.
- Via skin penetration, when a cat or person comes into contact with infective hookworm larvae in the environment.
- Ingestion or inhalation of infective third stage larvae.
- Cats can become infected in their mother’s uterus or when she nurses her kittens.
- Black or bloody stools due to bleeding in the intestines
- Anemia (weakness, pale gums)
- Poor coat condition
- Skin irritation, especially on the feet where hookworm larvae penetrate the skin
- Weight loss
- In kittens, stunted growth
Infection with hookworms presents as a red, extremely itchy, linear or snake-like eruption on the skin. Migration occurs at a rate of approximately 1cm a day. Most commonly affected areas are the feet, legs, buttocks, and hands but infection can occur on any part of the body which comes into contact with soil or sand. It is also possible to become infected after coming into contact with towels which have been sitting on the ground infected with hookworm larvae. It occurs mostly in tropical and sub-tropical areas.
Treatment in cats includes a suitable anti-worming medication and blood transfusion for severely anemic cats.
Roundworms (ascarids) are a common intestinal parasitic worm. There are two species which infect cats, Toxocara cati and Toxascaris leonina. Infection with T. cati is most common.
Roundworms feed upon the intestinal contents, competing with the host for food. They are around 3 – 5 inches long with a spaghetti-like in appearance. Both T. cati and T. leonina are found throughout the world.
- Direct ingestion of eggs from food or in the environment.
- Ingesting an infected transport host (such as a rat or mouse).
- Via the mother cat’s milk.
Humans become infected with roundworm by ingesting the eggs via contaminated soil (oral route) or larvae via raw/undercooked meat containing encysted larvae. Another route of infection is via fomites (contaminated objects such as towels). It takes several weeks before the eggs within the feces become infective in the soil.
Once ingested, eggs hatch into larvae and penetrate the walls of the digestive tract, migrating to various tissues in the body, this causes an inflammatory response. This migration is known as visceral larva migrans migrans or toxocariasis. Young children, especially those with pica are at greatest risk, although infection can occur in anybody.
There are a number of effective medications which can treat both species of roundworms. As they only work on adult roundworms, and not larvae or cysts. Therefore it is necessary to repeat treatment every two weeks as the larvae mature in the cat.
In humans, treatment may not be necessary where no symptoms are present. If treatment is required, antiparasitic medication such as albendazole will be prescribed.
While the list is quite extensive, it is possible to reduce or even prevent infection by taking a few simple steps.
- Keep your cat indoors, or provide access to a cat enclosure to prevent hunting.
- Cook meat thoroughly.
- Wash fruit and vegetables before consumption.
- Use a separate chopping board for meat and fruit/vegetables.
- Scoop out feces from litter trays at least once a day, preferably twice a day. Dispose of in the outside garbage.
- Do not empty litter trays outside in areas where food is grown.
- Always wash your hands after contact with a pet.
- Wear gloves when gardening and wash hands thoroughly when you have finished.