Lagochilascaris minor (Nematoda: Ascarididae) from a Wild Cougar (Puma concolor) in Mexico

The cougar, Puma concolor, is one of three large carnivore species in Mexico; its native distribution includes western Canada to southern Argentina and Chile (Chávez 2005; Ceballos and Arroyo-Cabrales 2012). Helminthologic studies related to cougars in Mexico are scarce. The recognized helminth fauna of the cougar is seven nominal species (Aelurostrongylus abtrusus, Physaloptera praeputialis, Spirocerca lupi, Spirometra mansonoides, Toxascaris leonina, Toxocara cati, and Uncinaria stenocephala) and nine unnamed taxa (Ancylostoma sp., Capillaria sp., Physaloptera sp., Strongyloides sp., Strongylus sp., Taenia sp., Toxocara sp., Trichuris sp., and Uncinaria sp.), identified mainly through egg morphology (García-Prieto et al. 2012). Here, we document an additional helminth species for the cougar, the nematode, Lagochilascaris minor, collected for the first time from an animal host in Mexico. Lagochilascariasis is an emerging zoonosis in Mexico, with at least five human cases reported (Vargas-Ocampo and Avarado-Aleman 1997; Román-López et al. 2003; Barrera-Pérez et al. 2012).

In December 2013, we collected 21 nematode specimens from an immature female cougar that had drowned in Laguna de Metztitlan, San Cristobal, Metztitlan, State of Hidalgo, Mexico (20°40′31.2″N, 98°51′14.3″W). Nematodes recovered were washed in 0.85% saline solution, fixed in 4% hot formalin, and cleared with Amman's lactophenol for taxonomic study; voucher specimens of parasites were deposited at the Colección Nacional de Helmintos (CNHE), Instituto de Biología, Universidad Nacional Autónoma de México, México City, Mexico.

We identified two nematode species parasitizing P. concolor: Lagochilascaris minor (CNHE 9989, one male and two females found in the esophagus) and Toxocara cati (CNHE 9990, 19 specimens collected in the intestine). The latter is a well-known parasite of wild and domestic felids. Taxonomic identification of L. minor follows Sprent (1971). Although in poor condition, several traits characteristic of the species were identified. The male was 6.63 mm long×97 μm wide at midbody, and the spicules were simple and equal in length (184 μm). The females were 8.2–9.0 mm long and 302–306 μm wide at midbody; the esophagus was 1.0–1.2 μm long; the distance from the anterior end to nerve ring was 327 μm; the vulva opening was at 3.2–3.3 mm from the anterior end; the ovejector was 171 μm long; eggs were 50–59 μm long and 49 μm wide; the mean number of surface pits in the eggshell at the circumference of the egg was 20; and the distance from the caudal extremity to the anus was 187–209 μm.

Lagochilascaris minor was described by Leiper in 1909, based on specimens removed from abscesses of two human patients from Port of Spain, Trinidad (Sprent 1971). In a review of the genus, Sprent (1971) recognized four species. Lagochilascaris minor is associated with humans, domestic cats (Felis catus; Fraiha-Neto et al. 1989), and silvatic carnivores in the Caribbean Islands, Central America, and South America (Brenes-Madrigal et al. 1972; Volcan and Medrano 1991). Lagochilascaris major is associated with lions (Panthera leo) in Africa (Leiper 1910), Lagochilascaris turgida with opossums (Lutreolina crassicaudata, Didelphis aurita, and Didelphis virginiana), in the Americas (Stossich 1902; Travassos 1924; Canavan 1931), and Lagochilascaris buckleyi with the American cougar (Puma concolor; Sprent 1971). More recently, two additional species have been described: Lagochilascaris sprenti from the Virginia opossum (Didelphis virginiana) in Louisiana, US (Bowman et al. 1983), and Lagochilascaris multipapillatum from the brown spotted viper, Trimeresurus mucrosquamatus, in China (Wang and Wang 1991).

Lagochilascaris minor differs from the other species of the genus in that the spicules are the smallest among the species of the genus (230–700 μm vs. 1,300 μm in L. buckleyi; 475–925 μm in L. major; 3,680–3,840 μm in L. multipapillatum; 750–1190 μm in L. sprenti; and 1,850 μm in L. turgida). In addition, L. sprenti and L. major have more surface pits in the eggshell at the circumference of the egg than L. minor (24–31, 35–45, and 15–25, respectively), and surface pits in L. buckleyi and L. turgida are relatively larger (Sprent 1971; Bowman et al. 1983; Wang and Wang 1991). We identified our specimens as L. minor based on the size of its spicules (0.184 μm) and mean number of surface pits (20).

Human lagochilascariasis is a zoonotic disease with neotropical distribution. Adult worms of L. minor are present in subcutaneous abscesses within the esophagus, pharynx, trachea, cervical lymph nodes, and lungs of the definitive host (Bowman et al. 2002). The disease is considered an emerging zoonosis in the Americas, spreading from Mexico to Argentina and the Caribbean Islands. Most human cases are from Brazil (81.2%), mainly in the Amazon region near forests and rural areas (Faccio et al. 2013). The route of infection for humans is poorly understood (Barrera-Pérez et al. 2012). Ingestion of raw or undercooked rodent meat is normally how humans become infected, but all patients denied consuming rodents. An alternative mode of infection may be from the ingestion of eliminated eggs from the definitive hosts. Five human cases of lagochilascariasis have been reported in Mexico, most from along the Atlantic coast (Yucatán and Veracruz; Vargas-Ocampo and Avarado-Aleman 1997; Barrera-Pérez et al. 2012), and one case from central Mexico (Estado de México; Román-López et al. 2003). This letter contributes to our understanding of the epidemiology of this zoonotic pathogen in Mexico.

We thank Georgina Ortega Leite for bibliographic support.