Aelurostrongylus abstrusus

Synopsis

CAPC Recommends

• First stage larvae are present in the feces of infected cats.
• Aelurostrongylus abstrusus is common in cats around the world.
• The cat appears to be the only definitive host; wild mice and other rodents, along with frogs, toads, snakes, lizards, and small birds, can serve as transport hosts.
• Prevention is through limiting interactions between cats and the intermediate and transport hosts.

Species

Feline

Aelurostrongylus abstrusus – feline lungworm.

Overview of the Life Cycle

• Eggs passed by adult female worms hatch in the lungs, and larvae pass up the trachea, down the intestinal tract, and out in the feces. Snail and slugs are the intermediate hosts, but the cat is probably infected by eating transport hosts, e.g., rodents, birds, amphibia, and reptiles. Ingested larvae are liberated in the intestine, penetrate the mucosa, and migrate to the lungs. Adult worms are found in the alveolar ducts and terminal bronchioles 8 to 9 days after infection.
• Egg laying starts about 4 weeks after infection. First-stage larvae are found in the feces about 6 weeks after the infection is initiated. Adults live 9 months or longer.

Stages

• The female is approximately 9 mm long, and the male 4 to 7 mm long. The vulva lies just anterior to the anus, and the tail ends bluntly. The ellipsoid egg in the lung measures approximately 80 μm.
• First-stage larvae are passed in the feces. The larvae are about 400 μm long, have “kinky” tail with a dorsal spine.
• The third-stage larva in the snail or transport host are the stage that infect the cat.

Disease

• Clinical signs are usually absent.
• Clinical signs may mimic other diseases including feline bronchial disease or asthma, verminous pneumonia, pulmonary edema, and pulmonary contusion.
• Nematodes and eggs may cause chronic coughing, dyspnea, open-mouth breathing, sneezing, wheezing or no clinical signs.
• Additional clinical signs include anorexia, weight loss and lethargy.

Prevalence

• Most common in cats that are allowed to hunt.
• Consistently found in cats throughout the world.

Host Associations – Transmission between Hosts

• This is a parasite of felidae.
• Other animals in a household are usually not at risk of obtaining infections due to the need for an intermediate host.

Prepatent Period – Environmental Factors

• First-stage larvae are found in the feces about 6 weeks after a cat is infected.

Site of Infection and Pathogenesis

• The adult worms live in the lungs; mature worms are found at the terminal parts of the bronchioles.
• Typical gross lesions consist of gray nodules, 1 to 10 mm in diameter, scattered over the surface of the lungs or arranged in clusters. Incised nodules exude a milky fluid that contains many eggs and larvae.

Diagnosis

• Diagnosis can be considered in cats with respiratory signs.
• Infection is confirmed by the demonstration of the first-stage larvae in the feces. This can be performed by fecal flotation, however morphological characteristics of the larvae may be distorted. A Baermann can also be performed on fresh fecal samples or sputum.
• First- stage larvae have been recovered via pulmonary fine-needle aspirate and visualized by Modified Wright’s stain.

Treatment

• Crisi et al (2017) indicated efficacy using fenbendazole 50 mg/kg q24h for 3 days.
• One study (Gambino et al., 2016) indicated efficacy using fenbendazole 50mg/kg PO q24h for 14 days along with prednisolone 0.5mg/kg PO q24h for 10 days to decrease inflammation due to death of the nematodes.
• Using imidacloprid 10%/moxidectin 1%, Crisi et al (2017) reported clinical recovery after 2 weeks in 11/12 cats, resolution of radiographic signs after 2 weeks in 7/12 cats with the remaining cats resolving at 4-6 weeks after treatment.
• Ivermectin has been used, but there has been a mixed set of results as to efficacy.

Control and Prevention

• Cats should not be allowed to hunt to prevent ingestion of the intermediate hosts, or more likely the transport hosts.

Public Health Considerations

• No human health hazard appears to be associated with Aelurostrongylus abstrusus.

References

• Crisi PE, Aste G, Traversa D, Di Cesare A, Febo E, Vignoli M, Santori D, Luciani A, Boari A. Single and mixed feline lungworm infections: clinical, radiographic and therapeutic features of 26 cases (2013-2015). JFMS Open Reports. 2017; 19: 1017-1029.
• Gambino J, Heiber E, Johnson M, Williams M. Diagnosis of Aelurostrongylus abstrusus verminous pneumonia via sonography-guided fine-needle pulmonary parenchymal aspiration in a cat. JFMS Open Reports. 2016; 2: 1-7.