Epidemiology, Infectious Diseases, Parasites, rare infectious disease

4 Parasite Infections From Your Pets and How to Prevent Them

Author Chandana Balasubramanian , 18-Apr-2024

Dogs, cats, birds, and other very pettable animals provide companionship and even help reduce anxiety and stress. Running and playing with your pets can lower your blood pressure and cholesterol, and caring for a pet can ease signs of depression.


However, you and your loved ones risk getting parasitic infections from your fur babies. 


Whether you’re a pet owner or just curious, read on to discover how these parasites spread and what steps you can take to protect yourself and your furry friends.


1. Toxocariasis (Roundworms)

Toxocariasis is caused by Toxocara spp., roundworms commonly found in mammals. These parasites are a significant health risk to humans, especially young children, and individuals who frequently come into contact with soil or pets [1].

Animal vectors or carriers

Toxocara primarily affects dogs and cats. Toxocara canis is commonly found in dogs, especially puppies, whereas Toxocara cati predominantly affects cats, including both wild and domestic varieties, with kittens being more susceptible [2].

These pets can easily spread the infection to humans without showing any symptoms themselves [2].

Mode of transmission

People can get toxocariasis in several ways. One common way is by swallowing eggs that are found in dirty environments, like soil or sand, or on objects that have touched animal poop. This is especially risky for kids who play in sandboxes or for people who garden or work with soil [1,2]. 

Eating undercooked meat from animals with the infection, such as rabbits or ducks, can also make people sick [1,2].


Many people with toxocariasis do not show symptoms, making the infection hard to detect without specific testing. However, in cases where the larval load is high, the larvae can penetrate the intestinal walls, enter the bloodstream, and travel to organs like the liver and lungs.

This condition, known as visceral toxocariasis, can cause a wide range of symptoms, including:

  • Fever
  • Weight loss
  • Cough
  • Rashes
  • Wheezing
  • Fatigue
  • Abdominal pain
  • Enlargement of the liver and spleen [3]. 


The larvae can live within human tissues for months, causing damage, but importantly, they do not mature into adult worms in humans [2]. 


2. Toxoplasmosis

Toxoplasmosis is a parasitic infection caused by the parasite Toxoplasma gondii, and it could be closer than you think—perhaps even in your own home with your pets. 

Toxoplasmosis can range from mild to severe, depending on the individual affected. Most healthy people who become infected with Toxoplasma gondii may not have any symptoms because their immune system keeps the parasite under control [4].

Animal vectors or carriers

Toxoplasmosis is primarily spread by cats, the definitive hosts for the parasite Toxoplasma gondii. While cats are essential to the parasite’s lifecycle, other animals, including livestock and wildlife, can carry the parasite in their tissues [4].

Mode of transmission

In cats, the parasite reproduces in the intestines and sheds oocysts—egg-like structures—in their feces. These oocysts are resilient and can survive in the environment for long periods, contaminating soil, water, and surfaces [5].

Humans and animals can become infected when they ingest these contaminated materials through activities such as gardening, playing in contaminated soil, or handling cat litter without proper hygiene [5].

Humans can also contract toxoplasmosis by consuming undercooked meat from infected animals [5].


Most individuals infected with the parasite exhibit no symptoms, but some may experience flu-like symptoms [6].

In pregnant women, toxoplasmosis can cause miscarriages or lead to congenital disabilities in the newborn. The risk of more severe illness is higher in newborns and individuals with compromised immune systems [6].

Symptoms of a more serious infection can include:

  • Fever
  • Seizures
  • Headaches
  • Nausea
  • Poor coordination [6].


3. Hookworms

Hookworms are parasitic nematodes (worms) that infect the intestines of their hosts, including humans, dogs, and cats.

These small, thread-like worms attach to the intestinal lining, feeding on blood and, in severe cases, leading to anemia and malnutrition. Hookworm infections are especially prevalent in warm, moist climates where sanitation and hygiene are poor [7].

Animal vectors or carriers

Dogs and cats can spread zoonotic hookworms through their feces [7].

Mode of transmission

Humans can contract zoonotic hookworms from their pets by touching soil that contains hookworm larvae from animal feces. When dogs and cats infected with hookworm pass hookworm eggs in their feces, these hardy eggs can last for even years in playgrounds, parks, and other areas.

Then, when people walk barefoot or touch the soil with their hands while gardening in areas where pets have defecated, they can get infected [8].

The larvae can enter through the skin, travel through the body, and settle in the intestines. To avoid this, it’s essential to wear shoes and gloves when working or playing in soil [8].


Common symptoms of a hookworm infestation include:

  • Itchy rash: This occurs when the larvae initially penetrate the skin, often causing a localized itchy reaction known as “ground itch” [7,9].
  • Abdominal pain: As the worms mature and attach to the intestine, they can cause discomfort or pain in the abdomen.
  • Diarrhea: Intestinal disturbances caused by the worms can lead to diarrhea, which may sometimes contain blood.
  • Fatigue and weakness: Hookworms feed on blood, which can lead to an iron deficiency (anemia), which causes fatigue, weakness, and, in severe cases, shortness of breath.
  • Weight loss and reduced appetite: Ongoing infection might lead to considerable weight loss and a decreased appetite due to the body’s nutrients being depleted.
  • Coughing: In some cases, as the larvae initially migrate through the lungs, individuals might experience transient respiratory symptoms like coughing or a feeling of chest discomfort [9].


4. Giardiasis

Giardiasis is the most common stomach infection caused by tiny parasites around the world. It affects about 2% of adults and 8% of children in developed countries [10].

Giardiasis is an intestinal infection caused by Giardia lamblia, often simply referred to as Giardia. This tiny protozoan parasite is commonly found in water sources and can infect both humans and animals [10].

Animal vectors or carriers

Pets, particularly dogs and cats, can transmit giardiasis to humans. Here’s how this happens:

  1. Dogs and cats: These pets can carry the Giardia parasite and shed its cysts in their feces. Humans can become infected by accidentally ingesting these cysts through direct contact with the feces of infected animals or by handling objects and surfaces that have been contaminated with these cysts [11].
  2. Other pets: While dogs and cats are the most common pet carriers, other animals, such as birds and small mammals like ferrets or guinea pigs, can also carry Giardia [11].


Mode of transmission

Transmission typically involves the fecal-oral route, where cysts shed in an animal’s feces are accidentally ingested through contaminated water, food, or surfaces [11]. 

Therefore, maintaining good hygiene, such as washing hands after touching pets or cleaning up their waste, is crucial for prevention [11].


Giardiasis, caused by the Giardia parasite, can lead to a variety of symptoms, including:

  1. Diarrhea: This is the most frequent symptom, often watery and sometimes foul-smelling.
  2. Stomach cramps: Pain and discomfort in the abdominal area are common due to the intestinal disturbance caused by the parasite.
  3. Bloating and gas: Excessive gas is produced when the parasite disrupts normal digestive processes.
  4. Nausea: Many people with giardiasis experience nausea, sometimes leading to vomiting.
  5. Fatigue: The body’s response to the infection and the potential for mild dehydration from diarrhea can lead to feelings of tiredness and weakness.
  6. Weight loss: Chronic cases of giardiasis may lead to weight loss due to decreased nutrient absorption and appetite [12].


Prevention and safety

To prevent parasitic infections in pets, pet owners can take several safety measures:

Preventing ingestion of infective eggs

  • Prevent children from playing in sandboxes contaminated with pet feces.
  • Practice good hygiene, especially washing hands after gardening or working with soil/dirt to avoid accidental ingestion of infective eggs [13].


Avoiding consumption of undercooked meat

  • Cook meat thoroughly to kill any encysted larvae. 
  • Be cautious when consuming meat from paratenic hosts like rabbits or ducks, as they can harbor infective larvae [13].


General hygiene practices

  • Regularly clean and disinfect areas where pets defecate to reduce environmental contamination.
  • Wear protective coverings such as gloves to clean litter boxes and wear covered footwear in exposed soil [13].


Education and deworming

  • Learn the risks of zoonotic parasites and the importance of deworming pets regularly.
  • Educate all household members on the significance of proper hygiene practices, like washing hands after handling pets or cleaning up after them [13].


Regular veterinary check-ups

  • Ensure pets receive routine veterinary examinations and follow deworming schedules recommended by the veterinarian.
  • Veterinarians can conduct fecal examinations to promptly detect and treat parasitic infections in pets, reducing the risk of transmission to humans [13].




Understanding how to prevent parasitic infections from spreading between pets and humans is crucial, particularly for pet owners and families. Diseases such as toxocariasis, toxoplasmosis, hookworms, and giardiasis underscore the hidden risks that can come from our furry friends. Managing these risks starts with maintaining rigorous cleanliness around pets and being vigilant about hygiene practices.

For instance, regularly cleaning areas where pets defecate can significantly reduce the risk of parasitic transmission. Wearing gloves while cleaning or handling pet waste and washing hands thoroughly afterward are simple yet effective steps. It’s also vital to keep pet areas clean and prevent kids from playing in potentially contaminated areas like sandboxes without proper supervision.


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Learn more about more parasitic infections on the GIDEON platform.


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[2]J.-F. Magnaval, E. Bouhsira, and J. Fillaux, “Therapy and prevention for human toxocariasis,” Microorganisms, vol. 10, no. 2, p. 241, 2022.
[3]“Toxocariasis,” Cdc.gov, 09-Jul-2019. [Online]. Available: https://www.cdc.gov/dpdx/toxocariasis/index.html. [Accessed: 18-Apr-2024].
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[5]S. K. Halonen and L. M. Weiss, “Toxoplasmosis,” in Neuroparasitology and Tropical Neurology, vol. 114, Elsevier, 2013, pp. 125–145.
[6]CDC-Centers for Disease Control and Prevention, “CDC – Toxoplasmosis – general information – frequently Asked Questions (FAQs),” 2010.
[7]A. O. Ghodeif and H. Jain, Hookworm. StatPearls Publishing, 2023.
[8]S. C. Parija, M. Chidambaram, and J. Mandal, “Epidemiology and clinical features of soil-transmitted helminths,” Tropical Parasitology, vol. 7, no. 2, p. 81, 2017.
[9]CDC-Centers for Disease Control and Prevention, “CDC – hookworm – general information – frequently asked questions (FAQs),” 2010.
[10]K. J. Esch and C. A. Petersen, “Transmission and epidemiology of zoonotic protozoal diseases of companion animals,” Clin. Microbiol. Rev., vol. 26, no. 1, pp. 58–85, 2013.
[11]N. Dunn and A. L. Juergens, Giardiasis. StatPearls Publishing, 2022.
[12]“General information,” Cdc.gov, 02-Mar-2021. [Online]. Available: https://www.cdc.gov/parasites/giardia/general-info.html. [Accessed: 18-Apr-2024].
[13]J. W. Stull, J. Brophy, and J. S. Weese, “Reducing the risk of pet-associated zoonotic infections,” CMAJ, vol. 187, no. 10, pp. 736–743, 2015.
Chandana Balasubramanian

Chandana Balasubramanian is an experienced healthcare executive who writes on the intersection of healthcare and technology. She is the President of Global Insight Advisory Network, and has a Masters degree in Biomedical Engineering from the University of Wisconsin-Madison, USA.

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