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May/June 2014 Today's Veterinary Practice 69 ParasiTe ProTocols | caNiNe PUlMoNarY HelMiNTHs tvpjournal.com Filaroides species Distribution. Infection with Filaroides species occurs sporadically, and periodically appears in some kennels or in indi- vidual dogs. 12 Life Cycle. Larvae shed in the feces or in the respiratory secretions of infected dogs are immediately infective and may be transmitted to other dogs by ingestion; this direct life cycle facilitates rapid spread between co-housed dogs. Ingested larvae migrate to the trachea and develop into adults in nodules (F osleri) or the lung parenchyma (F hirthi). Clinical Signs. Infection with F osleri can cause a hard, dry cough triggered by exercise or exposure to cold air. 12 Young dogs are most acutely affected and sometimes de- velop respiratory distress, anorexia, and emaciation. Infection with F hirthi is usually asymptomatic, but fatal cases of hyperinfection have developed in severely stressed and immunodeficient ani- mals. 13 Diagnosis. Infection with Filaroides species is di- agnosed by finding larva with fecal flotation using zinc-sulfate centrifugation. Larva of: 14 • F osleri have a constriction and a kink just posterior to the end of the tail (Figure 5). • F hirthi come to a simple point at the tip of the tail (Figure 6). Infection with F osleri may also be diagnosed at bron- choscopy by identifying the pathognomonic transparent submucosal nodules containing nematodes. Treatment (Table 2). The treatment of choice for F os- leri seems to be injectable doramectin; some veterinar- ians also remove as many nodules as possible with the aid of the bronchoscope. Dogs with both F osleri and F hirthi have also been successfully treated with several days of fenbendazole or iver- mectin. Prevention. Be- cause larvae of Filaroides species are immediately infective when shed in the feces, control can be difficult, particular- ly if other canine members of the household are infected. 15 Paragonimus kellicotti Distribution. Infection with P kellicotti occurs along the Mississippi, Missouri, Ohio, and St. Lawrence rivers and in areas of the southeastern U.S. 16 Life Cycle. Eggs passed in the feces hatch to release a miracidium, which penetrates a snail. Cercariae are pro- duced that leave the snail host and enter a crayfish to en- cyst as metacercariae. When the crayfish is eaten by a dog, cat, other wild carnivore, or a human, adult trematodes develop within cysts in the lung parenchyma. Paratenic hosts that ingest infected crayfish may also harbor infec- tive metacercariae. 1 Clinical Signs. Dogs infected with P kellicotti may be asymp- tomatic or can present with a variety of respiratory signs, including: • Coughing • Dyspnea • Bronchiectasis • Hemoptysis. Dogs may tolerate a low number of intact cysts, but in heavy infections, or when cysts rupture, severe disease may result due to: 17 • Pulmonary hemorrhage • Pneumothorax • Granulomatous pneumonia. Diagnosis. Eggs of P kellicotti can be recovered by sugar flotation, sedimentation of feces, or transtracheal wash, and are characterized by their size, seated operculum, and abopercular bump or flange on the end opposite the operculum (Figure 7). Pulmonary cysts may be evident on thoracic radiographs. Treatment (Table 2). Infec- tions may be treated with repeated courses of any of the following: 18 • Albendazole • Fenbendazole • Praziquantel. RISK FOR ZOONOTIC INFECTION Several of the common ca- nine pulmonary helminths are zoonotic, although in- fections are acquired from the environment or a vec- tor, rather than direct contact with infected dogs. • Toxocariasis upon ingestion of infective eggs of T canis from contaminated soil is well documented; as many as 1 in 7 adults in the U.S. harbor antibodies to Toxocara species. 19 • Human infection with D immitis via mosquitoes also occurs, resulting in development of pulmonary granu- lomata. 20 • Human infection with P kellicotti following ingestion of raw crayfish has also been reported in young men and is associated with alcohol consumption. 16 Figure 4. egg of Eucoleus aerophilus in feces, with typical polar plugs that are slightly askew of vertical between each end. Figure 5. Posterior end of tail of first-stage Filaroides osleri larva in feces, demonstrating the dorsal kink just terminal to the end of the tail. Figure 6. Posterior end of tail of first-stage Filaroides hirthi larva in feces, demonstrating the tapering conical tail. Figure 7. Paragonimus kellicotti egg in feces collected via sedimentation, demonstrating the seated operculum and the abopercular flange or bump. TVP_2014-0506_CAPC-CanineHelmiths_Part2.indd 69 5/24/2014 8:21:37 PM