Domestic animals face a variety of parasitic threats, from intestinal worms to skin-burrowing mites. These parasites can cause serious health issues, impacting animal welfare and productivity. Understanding common parasites is crucial for effective prevention and treatment.
Veterinarians must be familiar with parasite life cycles, transmission routes, and clinical signs to diagnose and treat infections accurately. From fecal tests to skin scrapings, various diagnostic methods help identify specific parasites. Treatment options range from broad-spectrum to targeted antiparasitic drugs.
Parasitic Infections in Domestic Animals
Common Endoparasites in Dogs and Cats
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Roundworms (, ) are prevalent intestinal parasites that can cause pot-bellied appearance, diarrhea, vomiting, and poor growth in puppies and kittens
Hookworms (, ) are blood-sucking parasites that can lead to anemia, diarrhea, and weight loss
Cutaneous larval migrans may occur in humans who come into contact with infected soil or sand
Whipworms () inhabit the cecum and colon, causing inflammation, diarrhea, and weight loss
Tapeworms (, Taenia spp.) are segmented parasites that can cause abdominal discomfort and visible proglottids in feces
Ectoparasites Frequently Affecting Dogs and Cats
Fleas () are common external parasites that cause itching, hair loss, and flea allergy dermatitis
Heavy infestations can lead to anemia, especially in young or small animals
Ticks (, ) are blood-sucking parasites that can transmit various diseases, such as Lyme disease, ehrlichiosis, and anaplasmosis
Mites, including (sarcoptic mange), (ear mites), and (demodectic mange), can cause skin irritation, hair loss, and secondary bacterial infections
Parasitic Infections in Livestock
Gastrointestinal nematodes, such as , , and , are common in cattle, sheep, and goats, causing anemia, diarrhea, and reduced production
(liver fluke) is a trematode that affects the liver and bile ducts of ruminants, leading to fascioliasis, which can cause weight loss, anemia, and sudden death
are protozoan parasites that cause , an intestinal disease characterized by diarrhea, dehydration, and weight loss in young animals
Coccidiosis is particularly problematic in intensive rearing conditions, such as poultry farms and cattle feedlots
Life Cycles and Transmission of Key Parasites
Direct Life Cycles
Roundworms (Toxocara spp.) have a direct life cycle, with eggs shed in feces and becoming infective in the environment
Transmission occurs through ingestion of infective eggs or transplacental and transmammary routes in
Hookworms (Ancylostoma spp.) also have a direct life cycle, with eggs shed in feces and larvae developing in the environment
Transmission occurs through percutaneous penetration of infective larvae, ingestion of larvae, or transmammary route in dogs
Haemonchus contortus, a gastrointestinal nematode of ruminants, has a direct life cycle, with eggs shed in feces and infective larvae developing in the environment
Transmission occurs through ingestion of infective larvae on pasture
Indirect Life Cycles
Dipylidium caninum, a common tapeworm in dogs and , has an indirect life cycle involving flea intermediate hosts
Pets become infected by ingesting infected fleas during grooming
, a protozoan parasite, has a complex life cycle involving felines as definitive hosts and various intermediate hosts
Transmission occurs through ingestion of oocysts from the environment or tissue cysts in infected prey or meat
Humans can become infected by ingesting oocysts from contaminated soil or water, or by consuming undercooked meat containing tissue cysts
Clinical Signs and Pathology of Parasitic Diseases
Gastrointestinal Parasites
Roundworm infections in puppies and kittens can cause pot-bellied appearance, diarrhea, vomiting, and poor growth
Heavy infections may lead to intestinal obstruction and even rupture
Hookworm infections can result in anemia, diarrhea, and weight loss in dogs and cats
Cutaneous larval migrans, characterized by serpentine tracks in the skin, may occur in humans who come into contact with infected soil or sand
Coccidiosis, caused by Eimeria spp., can cause diarrhea, dehydration, and weight loss in young animals, particularly in intensive rearing conditions
Severe infections can lead to mortality, especially in young or immunocompromised animals
Ectoparasites and Skin Diseases
Sarcoptic mange, caused by Sarcoptes scabiei mites, leads to intense pruritus, alopecia, and crusting of the skin in dogs
The mites burrow into the skin, causing inflammation and secondary bacterial infections
Demodicosis, caused by Demodex canis mites, can result in hair loss, skin redness, and scaling
Generalized demodicosis can be a serious condition, particularly in young or immunocompromised dogs
Flea infestations can cause itching, hair loss, and flea allergy dermatitis in dogs and cats
Heavy infestations can lead to anemia, especially in young or small animals
Systemic Parasitic Diseases
Haemonchosis in ruminants, caused by Haemonchus contortus, results in anemia, hypoproteinemia, submandibular edema (bottle jaw), and weight loss
Heavy infections can lead to death, particularly in young or stressed animals
Fascioliasis, caused by Fasciola hepatica, can lead to liver damage, weight loss, anemia, and sudden death in ruminants
Chronic infections may cause fibrosis and calcification of the bile ducts
Diagnosis and Treatment of Parasitic Infections
Diagnostic Methods
is a common diagnostic method for detecting helminth eggs and protozoan oocysts in fecal samples
Different flotation solutions, such as sodium nitrate or zinc sulfate, can be used depending on the parasite of interest
Fecal sedimentation techniques, such as the Benedect's sedimentation method, are used for diagnosing trematode infections like Fasciola hepatica
These techniques concentrate heavier parasite eggs that do not float well in standard flotation solutions
Skin scrapings and microscopic examination are used to diagnose ectoparasitic infestations, such as sarcoptic mange and demodicosis
The scrapings are examined under a microscope to identify the presence of mites or their eggs
Treatment Options
Anthelmintics are used to treat helminth infections in domestic animals
Macrocyclic lactones (ivermectin, moxidectin) are effective against a wide range of nematodes and some ectoparasites
Benzimidazoles (fenbendazole, albendazole) are used to treat nematode and some cestode infections
Tetrahydropyrimidines (pyrantel) are effective against roundworms and hookworms
Praziquantel is the drug of choice for treating tapeworm infections in dogs and cats
It is often combined with other anthelmintics in broad-spectrum deworming products
Anticoccidial drugs, such as sulfadimethoxine and toltrazuril, are used to control coccidiosis in and poultry
These drugs inhibit the development of the parasite, reducing the severity of the disease
and acaricides are used to control ectoparasitic infestations in companion animals
Fipronil, selamectin, and fluralaner are examples of topical or oral products that can be used to treat and prevent flea and tick infestations
Lime sulfur dips and ivermectin are often used to treat sarcoptic mange and demodicosis in dogs