Lung histopathology, radiography, high-resolution computed tomography, and bronchio-alveolar lavage cytology are altered by Toxocara cati infection in cats and is independent of development of adult intestinal parasites

Abstract

This study presents clinical findings after oral ingestion of Toxocara cati eggs which resulted in rapid pulmonary lung migration and parenchymal disease, noted on clinically relevant diagnostic methods. Further, the study investigated the efficacy of pre-infection applications of preventative medication on larval migration through the lungs. A third aim of the study was to determine if adult cats infected with T. cati developed lung disease. Cats in infected groups were administered five oral doses of L3 T. cati larvae. Four-month-old specific pathogen free (SPF) kittens were divided into three groups (six per group): an infected untreated group, an uninfected untreated control group, and an infected treated group (topical moxidectin and imidacloprid, Advantage Multi for Cats, Bayer Healthcare LLC). Six 2- to 3-year-old adult multiparous female SPF cats were an infected untreated adult group. The cats were evaluated by serial CBCs, bronchial-alveolar lavage (BAL), fecal examinations, thoracic radiographs, and thoracic computed tomography (CT) scans and were euthanized 65 days after the initial infection. Adult T. cati were recovered in infected untreated kittens (5/6) and infected untreated adults (5/6) in numbers consistent with natural infections. Eggs were identified in the feces of most but not all cats with adult worm infections. No adult worms were identified in the uninfected controls or the infected treated group. All cats in the infected groups, including treated cats and untreated cats without adult worms, had lung pathology based on evaluation of radiography, CT scans, and histopathology. The infected cats demonstrated a transient peripheral eosinophilia and marked eosinophilic BAL cytology, but normal bronchial reactivity based on in vivo CT and in vitro ring studies. Lung lesions initially identified by CT on day 11 were progressive. Thoracic radiographs in infected cats had a diffuse bronchial-interstitial pattern and enlarged pulmonary arteries. Pulmonary arterial, bronchial, and interstitial disease were prominent histological findings. Infected treated cats had a subtle attenuation but not prevention of lung disease compared to infected cats. Significant lung disease in kittens and adult cats is associated with the early arrival of T. cati larvae in the lungs and is independent of the development of adult worms in the intestine. These data suggest that while the medical prevention of the development of adult parasites after oral exposure to T. cati is obviously beneficial, this practice even with good client compliance will not prevent the development of lung disease which can alter clinical diagnostic methods.

Effect of pre-cardiac and adult stages of Dirofilaria immitis in pulmonary disease of cats: CBC, bronchial lavage cytology, serology, radiographs, CT images, bronchial reactivity, and histopathology

“…Thoracic radiographs were obtained on Days 0, 110, 168, and 240 and were graded for pulmonary artery size, tortuosity, blunting, bronchial pattern, interstitial pattern, and mixed bronchio-interstitial-alveolar pattern using a 0-3 system (0 = normal and 3 = severe lesions) Dillon et al, 2013). In addition, any abnormalities in cardiac, pleural, or diaphragm tissues were recorded.…”

“…Transverse sequential CT images of the lung (1 mm) were acquired and reconstructed using a detail and bone algorithm. The CT scans were graded as previously described (0-3 scale) (Dillon et al, 2013) as adapted from human and canine studies (Johnson et al, 2004(Johnson et al, , 2005. For CT evaluation, images were viewed in a lung window (W 1500, L 600).…”

“…In the software, automatic extraction of the lung is achieved by performing thresh holding using the Otsu Method (Otsu, 1979). The CT slices were exported into the COPDEmphysema module, and lung density histograms were obtained ranging from 300 to −1000 in Hounsfield units (HU) (Dillon et al, 2013). Distribution curves were generated for each and the frequencies of HU at −600, −856, −910, −925, and −950 were calculated.…”

Temporal Pattern of Circulating Antigens and Antibody Responses in Cats Experimentally Infected with Dirofilaria immitis

“…We propose that in this experimental model with infection of a large number of L 3 (100), the death of large numbers of immature worms may release adequate concentration of diagnostic antigen in the absence of mature female worms. Although this may lead to detectable antigenemia at time points more closely associated with HARD, similar results were not demonstrated in early detection of antigen in other experimental infections , Dillon et al 2013, Dillon et al 2014). …”

“…Currently available heartworm antibody tests can detect feline infection as early as 1 to 2 months after infection, and are useful as the infection develops in cats that may be antigennegative but have heartworms that have developed to at least the immature adult L4 stage (Lee et al 2010). However, antibody test sensitivity is unpredictable in cats with early as well as late infections (Snyder et al 2000) and may be positive in cats that are placed on preventative medications after initiation of the infection (Dillon et al 2013). …”