a 5-month - old feral kitten developed worsening respiratory signs , including tachypnea , coughing and wheezing after standard anthelmintic treatment with fenbendazole at a local shelter . the kitten was referred to the university of california , davis , william r pritchard veterinary medicine teaching hospital for further evaluation . thoracic radiographs revealed a severe diffuse bronchointerstitial pattern with bronchial cuffing , ill - defined nodules and lymphadenomegaly . bronchoalveolar lavage revealed marked neutrophilic and eosinophilic inflammation , and parasitic larvae were observed in a swab of trachea mucus . parasitic pneumonia should be considered as a cause of respiratory distress in kittens and cats . lungworm infections have been more commonly reported in free - roaming young and adult cats , but can not be excluded as a differential diagnosis in cats from varied environments and in kittens . kittens appear to be especially sensitive to lungworm infections , manifested by the development of more severe clinical signs ; thus lungworm infection should always be considered when presented with a kitten in respiratory distress . in the absence of cytologic confirmation of infection via bronchoalveolar lavage or oropharyngeal swab , pcr provides a valuable means for identification of lungworms , such as a abstrusus and troglostrongylus brevior . a 5-month - old female intact feral kitten presented to the local animal shelter unable to ambulate after being trapped underneath a garage door . a board - certified neurologist ( kmv ) localized the lesion to the c5 to brainstem region . cervical and thoracic radiographs showed no evidence of cervical fracture , but a mild bronchointerstitial pulmonary pattern was noted . as per routine protocol of the shelter , imidacloprid / moxidectin ( advantage multi for cats ; bayer ) was applied to the kitten and a 5 day course of fenbendazole was initiated at 50 mg / kg po q24h . the kitten was placed in foster care once able to ambulate 5 days later , and although it continued to improve neurologically , respiratory signs of tachypnea , cough and wheezing suddenly worsened in frequency and severity 9 days later . on day 10 , the cat presented to the university of california , davis , william r pritchard veterinary medicine teaching hospital for a further diagnostic work - up . on physical examination the kitten weighed 1.7 kg , heart rate was 180 beats per minute , respiratory rate was 70 breaths per minute with wheezing and rectal temperature was 103.0f . complete blood count results included a mild normocytic normochromic non - regenerative anaemia , likely age related ( haematocrit 27% ; reference interval [ ri ] 3050% ) , and a white blood cell count of 6098/l with neutrophils ( 4025/l ; ri 20009000/l ) , lymphocytes ( 1342/l ; ri 10007000/l ) and eosinophils ( 305/l ; ri 1501100/l ) within ris , and a slight left shift ( band neutrophils 183/l ; ri 0/l ) . mmol / l ) , hypochloremia ( 115 mmol / l ; ri 117126 mmol / l ) , hyperphosphatemia ( 9.0 mg / dl ; ri 3.26.3 mg / dl ) and increased alanine aminotransferase ( 103 thoracic radiographs revealed a severe diffuse bronchointerstitial pulmonary pattern with peribronchial cuffing and ill - defined pulmonary nodules . soft - tissue opacities dorsal to the carina and the second and third sternebrae were interpreted as lymphadenomegaly ( figure 1 ) . parasitic pulmonary disease was considered less likely due to previous treatment with fenbendazole and neoplasia ( lymphoma ) was also lower on the differential list . ( a ) lateral and ( b ) dorsoventral radiographs obtained on day 1 demonstrate a marked diffuse bronchointerstitial pulmonary pattern with peribronchial cuffing and ill - defined pulmonary nodules given the severity of thoracic radiographic findings , the kitten was prepped for anesthesia to undergo a laryngoscopy / bronchoscopy and bronchoalveolar lavage ( bal ) . premedication was provided with butorphanol 0.6 mg / kg ( 1.03 mg ) subcutaneously , flow - by 100% oxygen was provided and induction was performed with alfaxalone 1.0 mg / kg ( 1.7 mg ) and midazolam 0.3 mg / kg ( 0.5 mg ) intravenously . a jet ventilator was used to provide oxygenation at 180 pulses per minute , and anaesthesia maintained with an alfaxalone constant rate infusion to effect ( 4.12 mg / kg infused ) . a 2.8 mm outer diameter video - endoscope ( flex xc ; karl storz veterinary endoscopy ) was utilized for bronchoscopy . moderate laryngeal , tracheal and bronchial hyperemia was noted along with excessive mucus accumulation ( figure 2 ) . bal was performed in the left and right caudal lung lobes and was submitted for cytologic evaluation . copious amounts of tracheal mucus were expectorated and a swab collected from the oropharynx was also submitted for cytologic evaluation . ( a ) excessive pharyngeal mucus was observed on bronchoscopy and ( b ) the carina was diffusely reddened . * jet ventilator catheter bal fluid was hypercellular ( 1010 and 1100 cells/l , right and left , respectively ; ri 300400/l ) with 62% and 50% neutrophils ( normal 58% ) and 22% and 25% eosinophils ( normal < 20% ) ( figure 3 ) . increased numbers of multinucleate giant cells , goblet cells and mast cells were also present , along with epithelial hyperplasia . swabs of oropharyngeal mucus revealed a dense background of mucus with neutrophilic and eosinophilic inflammation , numerous free mucus granules and evidence of mineralization . five large parasitic ( helminth ) larvae were observed on one slide ( figure 4 ) , including one that appeared to have a dorsal spine on the tail . the oropharyngeal sample was submitted to the university of teramo for molecular identification of larvae . dna was extracted using a commercially available kit ( qiagen mini kit ; qiagen ) , and nested pcr was performed targeting the its2 region of aelurostrongylus abstrusus and troglostrongylus brevior , as previously described . pcr was positive for a abstrusus at the 233 base - pair region and negative for t brevior at the 356 base - pair region ( figure 5 ) . there are increased numbers of neutrophils and eosinophils , along with scattered macrophages and mast cells ( objective  60 , wright - giemsa stain ; bar = 10 m ) oropharyngeal swab cytology from a kitten with aelurostrongylus abstrusus lungworm infection . a helminth larva is present in a dense background of mucus with neutrophilic and eosinophilic inflammation ( objective  20 , wright - giemsa stain ; bar = 100 m ) pcr specific for the ribosomal its2 of aelurostrongylus abstrusus . lane m : gene ruler 100 base - pair marker ; lane 1 : oropharyngeal sample positive for a abstrusus ; lanes 2 and 3 : negative and positive controls for a abstrusus the kitten was discharged with application of a second dose of imidiclopid / moxidectin , and fenbendazole was prescribed at 50 mg / kg po q24h for 10 days . three weeks later , the kitten was doing clinically well at home but still coughing intermittently . radiographs revealed marked resolution in the bronchial pattern with partial resolution of peribronchial cuffing and ill - defined nodules ( figure 6 ) . fenbendazole was prescribed for an additional 5 days at 50 mg / kg / day . all respiratory signs had resolved at the time of ovariohysterectomy 3 weeks later , and radiographs 2 months after the final treatment were normal . ( a ) lateral and ( b ) dorsoventral radiographs obtained 3 weeks after a second course of fenbendazole ( 10 day course ) . the soft tissue opacity in the right caudal lung lobe lateral to the cardiac silhouette in ( b ) was considered to represent residual inflammatory infiltrate or a granuloma lungworm infection in domestic cats is most commonly caused by either a abstrusus or capillaria aerophila , although infection of domestic cats with t brevior is increasingly reported in europe . t brevior and a abstrusus have a similar indirect biological life cycle with estimated prepatent period of 46 weeks , while c aerophila has a direct life cycle . it is possible that t brevior , found primarily in the old world , might also be passed vertically in a transmammary fashion from queen to offspring . adults of a abstrusus reside within the alveolar ducts and alveoli , while t brevior live within the bronchi and bronchioles ; adults of c aerophila live within the submucosa of the trachea and bronchi . a abstrusus is considered the most common feline lungworm parasite and is found worldwide ; it can infect all cats , regardless of their habitat , lifestyle , breed or sex . indoor cats are at decreased risk , but possible infection should not be ruled out based upon lifestyle alone . kittens , owing to their immature immune system , and adult cats that hunt are at an increased risk for lungworm infection with a abstrusus . while lungworm infection most commonly affects young adult cats , 16% of infected cats were < 6 months of age in one study . clinical signs of infection vary depending upon worm burden , age , immune response and overall health status of the feline host , and can range from subclinical to severe disease , occasionally including fatal pneumonia . many cats are subclinical or can have respiratory signs of chronic cough with gradually increasing respiratory difficulty and tachypnea , wheezing , sneezing and nasal discharge , as well as anorexia and fever . kittens appear to develop more severe disease than adult cats , perhaps because of smaller bronchial diameter , which would be more susceptible to rapid occlusion of the airways by developing worms and concurrent inflammation . one case report describes a 2-month - old kitten that died from fatal verminous pneumonia and enteritis secondary to infection with a abstrusus , while another discusses reversible pulmonary hypertension in kittens secondary to infection with a abstrusus . kittens and young cats also develop more severe radiological abnormalities and higher larval worm burdens than adults . t brevior has been reported as an emerging helminth parasite in europe that can result in clinical signs similar to a abstrusus , although infection with the former lungworm is associated with more severe and life - threatening infection . kittens and young cats seem to be particularly susceptible to infection with t brevior , and clinical signs include severe cough , respiratory distress and nasal discharge . a more recent report describes the first known case of irreversible pulmonary hypertension in a kitten infected with t brevior , despite appropriate treatment . infection with c aerophila can be subclinical or associated with respiratory distress characterized by increased bronchovesicular sounds , wheezing , sneezing and a dry cough . diagnosis of lungworm infection can be challenging , as clinical signs often imitate other causes of respiratory signs , such as fungal infections , toxoplasmosis and feline asthma . radiographic abnormalities vary depending upon worm burden and time after onset of infection and range from a mild multifocal bronchointerstitial pulmonary pattern with poorly demarcated nodules ( often in the caudal lung lobes ) to a diffuse alveolar infiltrate . this test takes 24 h to complete , and three consecutive negative samples are required to rule out parasitic pneumonia . lungworm larvae can be found in tracheal swabs or washes , as well as on bal cytology , but sensitivity is not as high as with the baermann technique . infection with a abstrusus or t brevior can be documented by fecal baermann , and specific larval morphology can be used to differentiate the two organisms . feces , pharyngeal swabs and lower airway samples can be used for detection , but the best sample to submit for pcr appears to be a pharyngeal swab , which is supported by results in this case . while pharyngeal cytology and pcr have not been directly compared , pcr is reported to have a specificity of 100% and sensitivity of 96% . bal cytology was negative for the parasite in this case , indicating that additional ( pharyngeal ) samples may be needed to obtain a definitive diagnosis . this case was especially interesting because the kitten s clinical signs initially worsened after anthelmintic treatment . potential explanations include a severe immune response to a dying worm burden , a mixed infection or potentially a novel case of t brevior infection . a recent report described two littermates with mixed a abstrusus and t brevior infections that were treated appropriately with milbemycin oxime ( 2 mg / kg ) only to have one kitten develop fatal exacerbation of clinical signs . we consider it likely that worsening clinical signs noted in the kitten of this report were the result of an immune response to dying worms , which incited coughing , wheezing and tachypnea . given the marked inflammatory response present in bal cytology , treatment with corticosteroids could have been considered . this case serves as a clinically relevant reminder to include lungworm disease as a differential diagnosis when determining the cause of respiratory signs in cats , especially kittens and free - roaming cats or when the animal s history and origin are unknown . this case also supports the work currently being performed regarding improvement of diagnostics for feline lungworm , as it can be clinically difficult to diagnose . diagnosis of lungworm infection in this kitten was obtained via orophargyngeal swab cytology and pcr , with the latter being more sensitive and specific . diagnosis via cytology has a more rapid turnaround time , but differentiating t brevior from a abstrusus can be morphologically challenging . pcr allows both diagnosis and speciation ; however , this test is not yet readily available