Clinical Signs and Treatment of Intestinal Worms in Cats
Key Clinical Presentations
Cats with intestinal worm infections most commonly present with diarrhea, vomiting, weight loss, and visible worms in stool or vomitus, with Toxocara cati being the predominant parasite requiring immediate anthelmintic therapy. 1
Gastrointestinal Signs
Diarrhea is the hallmark symptom of intestinal parasitism, occurring significantly more often in infected cats (66.7%) compared to uninfected ones (19.2%). 1
Vomiting is strongly associated with Toxocara cati infection and may be the primary presenting complaint, particularly with gastric parasites like Ollulanus tricuspis. 1, 2
Weight loss occurs with chronic parasitism and heavy worm burdens, often accompanied by decreased appetite or inappetence. 1, 2
Visible worms in stool or vomitus are diagnostic—Toxocara cati adults appear as white, spaghetti-like worms 3-10 cm in length. 1
Additional Clinical Features
Abdominal distension may be present in kittens with heavy roundworm burdens. 1
Poor body condition and failure to thrive are common in young cats with parasitism. 1
Perianal irritation can occur but is less prominent than in dogs. 1
Asymptomatic carriage is common—many infected cats show no clinical signs, particularly adult cats with light infections. 3, 1
Specific Parasites and Their Presentations
Toxocara cati (Roundworm)
Most prevalent intestinal parasite in cats, found in 40.2% of infected animals and 53.3% of symptomatic cats. 1
Risk factors include lack of deworming in the last 3 months (OR: 15.9), outdoor access (OR: 13.8), presence of digestive symptoms (OR: 5.4), and young age (OR: 4.2). 1
Clinical signs include vomiting, diarrhea, and inappetence regardless of age. 1
Giardia duodenalis (Protozoan)
Acute small bowel diarrhea with occasional weight loss is the typical presentation, though most infected cats remain asymptomatic. 3
Diagnosis is challenging but improved with commercially available ELISA kits. 3
Cystoisospora spp. (Coccidia)
Found in 10.2% of infected cats and significantly more common (15.6%) in symptomatic animals. 1
Associated with diarrhea in young cats. 1
Ollulanus tricuspis (Gastric Worm)
Vomiting is the main presenting sign, with weight loss as a secondary complaint. 2
Endoscopic appearance of the stomach is typically normal despite chronic gastritis on histology. 2
Diagnostic Approach
Fecal Examination
Flotation method using sodium chloride saturated solution is the standard diagnostic test for most intestinal parasites. 1
Three consecutive daily samples should be collected to maximize sensitivity, as single samples may miss infections. 4
Fecal ELISA for Giardia antigen provides improved diagnostic accuracy over microscopy alone. 3
Additional Diagnostics
Complete blood count may reveal eosinophilia in some helminth infections, though this is less pronounced in cats than in humans. 4
Endoscopic biopsy may be required to diagnose gastric parasites like Ollulanus tricuspis when other tests are negative. 2
Blood examination is essential when evaluating chronic diarrhea to assess for systemic involvement. 5
Treatment Protocols
Toxocara cati and Hookworms
Albendazole 400 mg PO as a single dose is first-line treatment for most intestinal worms in humans, but dosing must be adjusted for feline body weight (typically 25-50 mg/kg). 6
Mebendazole 500 mg PO as a single dose is an alternative, with feline dosing adjusted appropriately. 7
Ivermectin 200 μg/kg PO as a single dose can be used for roundworms and hookworms. 7
Giardia duodenalis
Combination therapy with fenbendazole and metronidazole is recommended as the safest and most effective treatment for symptomatic cats. 3
Environmental control and supportive measures are essential adjuncts to drug therapy. 3
Tapeworms (Taeniidae)
Praziquantel 10 mg/kg PO as a single dose is effective for tapeworm infections. 7
Niclosamide 2 g PO as a single dose is an alternative, though dosing must be adjusted for cats. 7
Cystoisospora spp.
Supportive care with fluid therapy and dietary management is often sufficient for mild cases. 5
Specific anticoccidial therapy may be required for severe infections. 5
Critical Management Considerations
Treatment Timing and Follow-up
Immediate treatment is indicated for symptomatic cats with confirmed or suspected parasitism. 1
Repeat fecal examination 2-4 weeks post-treatment confirms parasite clearance. 3
Regular deworming every 3 months significantly reduces infection risk. 1
Environmental and Household Management
Treat all household cats simultaneously to prevent reinfection, particularly for highly contagious parasites. 6
Environmental decontamination includes removing feces daily and cleaning litter boxes with disinfectants. 3
Prevent outdoor access when possible to reduce exposure to soil-borne parasites. 1
Special Populations
Kittens are at highest risk for heavy worm burdens and should be dewormed starting at 2-3 weeks of age. 1
Immunocompromised cats require aggressive treatment and close monitoring. 8
Pregnant queens should be dewormed to prevent transmission to kittens. 1
Common Pitfalls to Avoid
Never assume a single negative fecal test excludes parasitism—sensitivity is only 50% for many helminths with single samples. 4
Do not delay treatment in symptomatic cats while awaiting fecal results if clinical suspicion is high. 1
Avoid empiric corticosteroids for chronic diarrhea without first ruling out parasitism, as immunosuppression can worsen infections. 5
Do not overlook zoonotic potential—Toxocara cati poses significant public health risk, particularly to children. 1
Never use ivermectin in cats without confirming safety—some formulations and doses can be toxic to felines. 7