Category:Cat Nematodes

Nematodes of Cats

In the UK, the only nematodes commonly found are Toxocara cati and, to a lesser extent, Toxascaris leonina. Hookworm infections are reported on rare occasions, but it is not known which species this is. The metastrongyloid lungworm of cats, Aelurostrongylus, can be problematic as the prognosis is guarded once clinical signs appear. Overseas, cats have their own species of hookworm and whipworm, and may be at risk from canine heartworm in highly endemic areas.

Toxocara cati

• The biology of T. cati is generally similar to that of T. canis, except that there is no prenatal transmission.
• Adults can establish in cats and other felidae.
• The prepatent period is about 8weeks.
• Somatic larvae can accumulate in a wide range of paratenic hosts.
• Larvae have been recovered from human tissues on rare occasions, but its role in VLM and OLM is unknown.

Toxascaris leonina

• Infects canidae and felidae (see under Dog Nematodes).

Aelurostrongylus abstrusus

• The cat lungworm - a typical metastrongyloid.
• Adults are small (approximately 1cm), and live in the lung parenchyma and small bronchioles.
• Life-Cycle:

→ L1 with kinky tail in faeces

→ mollusc intermediate host

→ cat infected either by eating an infected mollusc, or by eating a paratenic host that has eaten an infected mollusc

• Infections often asymptomatic, but can cause serious respiratory problems, especially in immunocompromised cats.

Dirofilaria immitis

• A canine parasite - see under Dog Nematodes for life-cycle etc.
• Cats are abnormal hosts, and so D. immitis is not very infective for cats.
• Nevertheless, feline infection is common (up to 25%) in some heavily endemic areas.
• But only small numbers of adult worms (1-3) establish.
• The prepatent period is longer (approximately 8months) than in the dog.
• Few, if any, microfilariae are produced (<20% of cases positive).
• The life-span of the worm is shorter (2-3years).
• However: one dead adult → acute pulmonary crisis (thromboembolism).

Feline Heartworm Disease

• Lung pathology similar to dog, but little heart pathology.
• Coughing starts 4-6months post-infection.
• Antibody-detection ELISA used for diagnosis, but false positives occur (antigen ELISA cannot be used as antigen rarely expressed in cats).
• There is no licensed adulticidal therapy, and treatment may be fatal for the cat as well as the worm.
• Ivermectin or selamectin can be used for prevention.

Lungworms of Dogs and Cats

Aelurostrongylosis

• Often asymptomatic; serious respiratory problems usually due to deficient immunity.
• Prognosis poor.
• Post mortem examination reveals greenish nodules in lungs.
• Histopathology diferentiates these from tuberculosis.

Angiostrongylosis

• Clinical signs of angiostrongylosis are associated with:
  • accumulating lung damage caused by eggs and larvae (respiratory distress)
  • coagulation disorders caused by adult worms (bruising, haematomas, e.g. in spinal cord)
• Diagnosis: demonstration of large numbers of L1 in faeces (with Barmann technique).

Filaroides Infections

• F. osleri is usually associated with particular boarding kennels.
• Diagnosis and treatment are difficult.
• The Baermann apparatus is used to recover L1 from faeces.
• Larvae are, however, few in number and have sluggish movements.
• They may, therefore, be very difficult to demonstrate in faeces or sputum.
• Endoscopy (to visualise the tracheal nodules) is often required to confirm diagnosis.

Treatment of Lungworms in Dogs and Cats

• Angiostrongylus vasorum is easy to treat with suitable anthelmintics, but the others require high daily doses of benzimidazoles for 3-7days.
• Two or more courses of treatment may be necessary (with a rest period between each).
• Fenbendazole is licensed for the treatment of Aelurostrongylus (50mg/kg for 3days) and F. osleri (50mg/kg for 7days).