Parasites are major causes of respiratory tract disease in the dog and cat. Recent advances in therapy of these diseases have been made providing the practicing veterinarian with a more rational treatment modality.
Parasites are major causes of respiratory tract disease in the dog and cat. Recent advances in therapy of these diseases have been made providing the practicing veterinarian with a more rational treatment modality. This review will discuss the biology, diagnosis, disease, and treatment of respiratory parasites (protozoan, nematode, trematode, and arthropods) of the dog and cat. Emphasis will be placed on the use of modern chemotherapeutic agents in their control. The parasites will be discussed based on their location within the respiratory system; nasal mucosa and sinuses, lung parenchyma, and airways.
Epidemiology: Arthropod dipteran parasite; some 34 different species in North America.
Clinical signs: Depend mainly on where the larva locates.
Diagnosis: Viewing the larvae within the respiratory tract, or made on circumstantial evidence of acute rhinitis (sometimes progressing to neurologic disease) in an outdoor cat during late summer and fall. The larvae or its migration tracts through the brain may be identified on CT scan or MRI.
Treatment: Ivermectin (0.1 to 0.3 mg/kg, PO, q24h, 3 days) very effective.
Epidemiology: Arthropod parasite of nasal sinuses of dogs. Occurs in the USA, Canada, Japan, Australia, Sth. Africa and Europe.
Clinical signs: Sneezing, although can present with facial pruritis, snuffling, snorting + nasal discharge and excessive lacrimation.
Treatment: Ivermectin (200 µm/kg body weight, PO or SC) or Milbemycin (0.5 mg/kg, PO) once weekly for 3 weeks are effective.
Epidemiology: Pentastomid parasites that represent a group of specialized crustacean-like arthropods.
Clinical signs: Sneezing, slight nasal discharge sometimes containing blood. The parasites become large, lie in the recesses of the nasal turbinates, and attach themselves firmly to the mucous membranes with their four hook. The adults apparently feed on respiratory mucosal cells and blood. When fully grown, the parasites are capable of causing nasal obstruction.
Diagnosis: Eggs (yellowish oval, 80 m, surrounded by bladder-like envelope and containing a four-legged larva) in the nasal secretions. - identifying larvae during rhinoscopy.
Treatment: Physical removal only treatment described. Ivermectin (200 µg/kg, PO, once) may be efficacious.
Epidemiology: Capillarid nematode parasite of nasal mucosa of the dog. Adult worms live threaded through the mucosa of the nasal sinuses. Adults appear as very fine threads seen grossly as very fine transparent hairs.
Clinical signs: Sneezing, nasal discharge.
Diagnosis: Identifying eggs in feces (eggs can be recovered in nasal washings).
Treatment: Fenbendazole (50 mg/kg, PO, q24h, 7 days). Ivermectin (200 µg/kg, PO, once).
Epidemiology: Metastrongyloid nematode parasite of cats.
Clinical signs: Heavy infestations (100 larvae) can cause severe pulmonary disease and radiographic changes by 2-wks PI. Most severe disease occurs 5 to 15 weeks after infection.
Diagnosis: Identifying typical larvae in the feces or in a trans-tracheal wash.
Treatment: Fenbendazole (20 mg/kg, PO, q24h, for 5 days, then repeat after 1 week).
Epidemiology: Trichuroidea parasite with bi-operculate eggs. Direct life cycle.
Clinical Signs: Fairly common infection in both cats and dogs.
Treatment: Assymptomatic cases do not require treatment.
Epidemiology: Metastrongyloid nematodes found in the lung parenchyma of dogs. Direct life cycle.
Clinical signs: Nonproductive cough + increased respiratory rate.
Treatment: Albendazole (25 mg/kg, PO, q12h, 5 days, then repeat treatment 2 wks later).
Epidemiology: Trematode (fluke) normally found in mink, but occasionally in the lungs of dogs and cats.
Clinical signs: Most are asymptomatic but those with disease present with a chronic cough (unresponsive to most treatments) and rarely pneumothorax.
Diagnosis: Identifying eggs (large, operculated) in feces or tracheal wash. Radiology; multiloculated cysts (dogs), and interstitial nodules (cats).
Treatment: Praziquantel (23 mg/kg PO, q8h, 3 days), or fenbendazole (50 mg/kg PO, q24h, 10-14 days).
Epidemiology: Metastrongyloid nematode of bronchi (dogs and other canids). Adult worms (males; 4 to 8 mm long, females; 12 to 16 mm long) parasitize the terminal bronchi of the respiratory tract where eggs are laid, develop and hatch, larvae then coughed up and swallowed to be passed in the feces.
Clinical signs: Infection occurs during summer in dogs living or visiting rural areas frequented by foxes, the more usual definitive host. - dry, nonproductive cough easily elicited by tracheal palpation. Cough may be chronic and productive.
Diagnosis: Larvae (pointed tail, 250 - 300 um) in feces or tracheal wash sample.
Treatment: Fenbendazole (50 mg/kg PO, q24h, 3 days, or 20 mg/kg, PO, q24h, 14 days).
Epidemiology: Metastrongyloid nematode: causing nodules in the terminal trachea and bronchi of dogs and other canids (coyotes, foxes). Adult worms found in subepithelial fibrous nodules usually close to the bifurcation of the trachea and extending down into the mainstem bronchi. Thin-shelled eggs or larva (L1 - infective stage and very similar to F. hirthi) are coughed up, swallowed, enter feces, or coat regurgitated food.
Clinical signs: Dry cough (often precipitated by exercise or tracheal palpation) unresponsive to antibiotics or
steroids.
Diagnosis: L1 in fecal samples or in transtracheal washes. Bronchoscopy: identifies the brown reddy nodules at the tracheal bifurcation. Radiology may reveal soft tissue nodular densities at the tracheal bifurcation.
Treatment: Physical removal of nodules via bronchoscopy can be life saving.
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Gunnarsson LK, Moller LC, Einarsson AM, et al. Clinical efficacy of milbemycin oxime in the treatment of nasal mite infection in dogs. J Am Anim Hosp Assoc 1999;35:81-84.
Barr SC. Feline Lungworm (Aelurostrongylus). In: Canine and Feline Infectious Diseases and Parasitology. Barr SC and Bowman DD (eds). Ames Ia: Blackwell Publishing. 2006. p. 233.
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Barr SC, Lavelle RB, Harrigan KE, et al. Oslerus (Filaroides) osleri in a dog. Aust Vet J 1986;63:334-336.
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