Of the 43 free-ranging animals examined, 36 cats and 7 dogs, collected between 2018 and 2023, 21 cats and 7 dogs were found parasitized with helminths; the collected helminth species belong to the phylum Platyhelminthes and Nematoda. In cats, the cestodes Hydatigera taeniaeformis, Mesocestoides sp., Taenia rileyi and the nematode Toxocara cati were recorded, while in dogs, the cestode Taenia pisiformis and the nematodes Ancylostoma caninum, and Uncinaria stenocephala were found. The cestode D. caninum is the only shared species among these mammals and reaches the highest prevalence in dogs, while the nematode T. cati was the most prevalent in cats. With the exception of Mesocestoides sp. in cats, both helminth mean abundance and mean intensity were higher in dogs (Table 2).
Table 2
Infection parameters of helminths in free-ranging dogs and cats from the Reserva Ecológica del Pedregal de San Ángel in Mexico City, Mexico.
Helminths species | Canis lupus familiaris | Felis silvestris catus |
Cestoda | Prevalence | Mean abundance | Mean intensity | Intensity range | Prevalence | Mean abundance | Mean intensity | Intensity range | Prevalence |
Dipylidium caninum | 71.42 | 8.28 | 11.6 | 3–25 | 19.44 | 1.58 | 8.14 | 1–21 | 57 |
Hydatigera taeniaeformis | | | | | 19.44 | 0.47 | 2.42 | 1–6 | 17 |
Taenia pisiformis | 57.14 | 20.57 | 36 | 1-138 | | | | | |
Mesocestoides sp. | | | | | 19.44 | 17.86 | 91.85 | 1-450 | 643 |
Taenia rileyi | | | | | 11.11 | 0.19 | 1.75 | 1–4 | 7 |
Nematoda | | | |
Toxocara cati | | | | | 50 | 4.58 | 9.16 | 1–26 | 165 |
Ancylostoma caninum | 42.85 | 4.85 | 11.33 | 5–22 | | | | | |
Uncinaria stenocephala | 28.57 | 5.42 | 19 | 17–20 | | | | | |
Based on the morphological and molecular studies carried out, the diagnostic characteristics of each of the 8 species found are presented below, briefly discussing the criteria followed for their identification:
Cestoda
Taeniidae
Hydatigera taeniaeformis Batsch, 1786
Material: CNHE: 11833, 13003. cox1 GenBank: OQ281682, OQ281678, PP574870; 28S GenBank: OQ413990.
Diagnosis
Based on 15 individuals. Scolex with armed rostellum with 2 crowns of 30–40 hooks (35.5 +/- 4.43; n = 5), larger hooks 306–430 (420 +/- 0.017; n = 52); smaller hooks 250–270 (270 +/- 0.010; n = 57) in length (Fig. 1a – d). Testes in mature proglottids are 278–544 (384.6+/- 81.94; n = 15).
Remarks
Specimens were identified based on the number and size of large and small hooks in the 2 crowns of the rostellum, according to Esch and Self (1965) for canids and felids from USA; Panti-May et al. (2019, 2023) for rodents from Mexico, and Lavikainen et al. (2016) for rodents and cats from several countries around the world. Blastn search of cox1 gene results in identical sequences to H. taeniaeformis from Peru (OQ569222-OQ569229) found in rodents (Gómez-Puerta et al. 2023). Likewise, there is a relatively high similarity (up to 98%) with the rest of the sequences published in GenBank from other parts of the world (Lavikainen et al. 2016), corroborating the global occurrence of this species.
Taenia pisiformis Bloch, 1780
Material: CNHE: 13001-2. coxI GenBank: PP472462; 28S GenBank: PP574874.
Diagnosis
Based on 11 specimens with scolex with two crowns of 42–46 hooks (43.82 +/- 1.40; n = 11) on the rostellum; hooks of anterior row 240–260 (250 +/- 0.0060; n = 129) in length, and hooks of the second row 140–150 (150+/- 0.0057; n = 125) in length (Fig. 1e – h). Testes in mature proglottids are 200–366 (275.77+/- 50.08; n = 13). Gravid proglottids with 14–24 (19.17 +/- 3.43; n = 6) uterine branches.
Remarks
The morphologic traits of rostellar hooks, which number and size are in accordance with those recorded by Riser (1956) for this cestode parasitizing felids from USA; Verster (1969) and Loos-Frank (2000) for different species worldwide and by Esch and Self (1965) for canids and cats from USA, allowed the identification of this species. Blastn search resulted in low similarity with the sequences previously published for both T. pisiformis and other species of Taenia, with similarities ranging from 88–91% with 28S locus. In the same way, cox1 blastn search resulted in the highest similarity (92.04%) with a sequence obtained from a cysticercus of T. pisiformis from Poland (MZ287426) found in a rabbit (Samorek-Pierog 2021). The wide genetic variation detected in this study suggests that this cestode species may represent a complex of more than one species, or alternatively, that the DNA sequence of T. pisiformis available in Genbank are result of a morphological misidentification.
Taenia rileyi Loewen, 1929
Material: CNHE: 12997-98. cox1 GenBank: PP574871.
Diagnosis
Based on seven scolices with two rows of 34–46 (41.33 +/- 7.0710; n = 5) hooks on the rostellum, larger hooks 220–240 (230 +/- 0.00538; n = 46), and smaller hooks 150–180 (170 +/- 0.00885; n = 43) (Fig. 1i – l).
Remarks
The number of hooks and their measurements fit with the wide variability range reported for this species by different authors in several hosts throughout their distribution; according to the above, the number of hooks reported for T. rileyi ranges from 36 to 46; the size of the largest ones oscillates from 205–258 and the smallest ones from 151 to 205 [Riser (1956); Mollhagen (1979); Rausch (1981); Loos-Frank (2000) and Panti-May et al. (2023)]. Blastn search recovered Taenia sp. as the first match with 90.38% of similarity, with specimens recovered from wild cats from Colombia (MZ351293) (Uribe et al. 2021). Sequences generated in the present study represent the first cox1 sequence for this species of cestode.
Dipylidiidae
Dipylidium caninum (Linnaeus, 1758) Leuckart, 1863
Material: CNHE 10977, 11875. cox1 GenBank: OQ281679; 28S GenBank: OQ401031
Diagnosis
Based on 21 specimens with scolex with a protrusible rostellum armed with 75–90 (84 +/-7.93; n = 3) hooks, distributed in 3–6 rows, hooks length between 0.006–0.015 (11 +/- 0.003; n = 146) (Fig. 1m – o). Mature proglottids with 103–277 (195.62 +/- 42.66; n = 71) testes; two sets of genitalia. Gravid proglottids contain numerous ovigerous capsules with 4–15 (7.69 +/- 2.08; n = 155) eggs each; eggs diameter ranging from 1–3 (1.90 +/- 0.91; n = 115).
Remarks
Adults specimens were identified on the basis of the features of rostellum, such as having uniformly thorn-like hooks distributed in several rows, vaginal opening posterior to cirrus sac and because each ovigerous capsules contain several numbers of eggs (Khalil et al. 1994). These characteristics have also been referred as diagnostic for the species by Venard (1936) in parasites from dogs and cats from USA; for dogs, cats and humans from Mexico (Lamothe-Argumedo and García-Prieto 1988; Cabello et al. 2011); India (Ramana et al. 2011; Narasimham et al. 2013; Sivajothi and Reddy 2018); China (Jiang et al. 2017) and Portugal (Rousseau et al. 2022); Blastn search of cox1 gene resulted in identical sequences for D. caninum from Italy (MT806359) found in red foxes (Citterio et al. 2021). In the same way, 28S gen query resulted in identical sequences to D. caninum from several localities of Europe, South Africa and USA (MH040824- MH040861, MH045472- MH045481) found in dogs and cats (Labuschagne et al. 2018).
Mesocestoididae
Mesocestoides sp.
Material: CNHE: 12995-6. cox1 GenBank: OQ281680, OQ281681; 28S GenBank: OQ343502. (Fig. 2).
Diagnosis
Based on 15 unarmed scolices and 26 proglottids. Scolex with 4 round suckers (Fig. 2a,b). Mature proglottids contain 38–51 (46.12 +/- 4.55; n = 8) testes. Gravid proglottids with paruterine organ [(0.273–0.464 (0.35+/-0.05; n = 18) length by 0.209–0.382 (0.30+/-0.04; n = 18) width, and 0.018–0.046 (0.03+/-0.01; n = 18) wall thickness]. Central genital pore.
Remarks: Adult worms collected in free-ranging cats present morphological features diagnostic of Mesocestoides such as cirrus-sac and vaginal duct opening in a genital atrium toward ventral surface of proglottid midline; vitelline gland bilobed, and uterus replaced by a single paruterine organ, according to Khalil et al. (1994) and Caira and Jensen (2017). According to Caira et al. (2022), four species of Mesocestoides are valid: M. ambiguous Vaillant, 1863 from Africa ex. Vivera genetta; M. corti Hoeppli, 1925 ex. Mus musculus from the USA; M. melesi Yanchep and Petrov, 1985 ex. Meles sp. from Bulgaria and M. vogae Edges 1991 ex. Sceloporus occidentalis from USA. In Mexico, only 2 species have been described: M. vogae ex Canis lupus familiarias (Eguia et al. 2005) and M. bassarisci McCallum 1921 ex Basssariscus astutus (McCallum 1921), but the validity of the latter has not been confirmed (Caira et al. 2022).
The cox1 and 28S sequences blast analyses resulted in 91.47% and 97.07% of identity, respectively, with sequences deposited in GenBank for species of this genus that parasitize rodents (NC_061204) from China (Wu et al. 2022), and domestic mammals (MK239661) from Europe and Africa (Heneberg et al. 2019), respectively. Excepting for M. ambiguous, the sequences of three of the species mentioned above have been deposited in GenBank, but none match the sequences generated here.
Nematoda
Ascarididae
Toxocara cati (Schrank, 1788) Brumpt, 1927
Material: CNHE: 11832. ITS GenBank: OQ256234; 28S GenBank: OQ343501
Diagnosis: Based on twenty-eight specimens (fifteen females and thirteen males). Both sexes with a pair of cervical alae, which give the anterior end of the body an arrow-like appearance. Mouth located anteriorly with three lips, one large dorsal and two smaller ventro-lateral. Dorsal lip has two large papillae; each ventrolateral lip has only one. Dentigerous ridges arranged on the margin of each lip. Females: body 4.5–8.2 mm (6.9 mm +/- 1.21; n = 12) long by 0.88–2.04 mm (1.33 mm +/-0.36; n = 12) wide; distance between the anus and the anterior end of the body 0.43–0.64 mm (0.56 mm +/-0.07; n = 12). Males: body 3.5–6 mm (5.2 mm +/- 0.79; n = 11) long by 0.81–1.48 mm (1.21 mm +/-0.22; n = 11) wide. Genital papillae, distributed as follows: 12–22 (17.75 +/-3.28; n = 12) precloacals, 2 (n = 12) adcloacals and 4 (n = 12) postcloacals. Paired spicules, 1.97–2.68 mm (2.19 mm +/- 0.22; n = 17) (Fig. 3a – c).
Remarks
Adult worms collected in the free-ranging cats studied were identified at specific level based on the features in anterior and posterior ends of body in males and females. Anterior section lips well-defined in both sexes, a pair of spicules and several cloacal papillae in posterior end of males. All these traits agree with those presented in the re-description of the species made by Sprent (1956) for parasites of cats from Australia; Gallas and Fraga (2013) from wild felines from Brazil; Radwan et al. (2009) for canids and felines from Egypt and Mekete (2003) for cats from South Africa. Blastn query of 28S sequence results in a similarity of 99.51% with specimen found in wild cats from China (JN256994) (Li et al. 2012), and 100% for ITS (MF592398) with a specimen from Iran (Choobineh et al. 2018) found in soil samples with eggs of Toxocara.
Ancylostomatidae
Ancylostoma caninum (Ercolani, 1859)
Material: CNHE: 12999. cox I GenBank: OQ290602; ITS GenBank: OQ256235, OQ256236.
Diagnosis: Based on 34 individuals (twenty-one females and thirteen males). Mouth opening with a pair of prominent chitinous plates provided with three pairs of ventral teeth. Females: body 0.4–1.5 mm (1.11 mm +/- 0.28; n = 20) length by 0.26–0.63 mm (0.49 +/- 0.11; n = 19) wide; vulva at the posterior end of the body, which ends in a spine; distance between anus and tail 0.15–0.25 mm (0.21 mm +/-0.03; n = 19). Males: body 0.2–1.1mm (0.96 mm +/- 0.25; n = 11) length by 0.29–0.50 mm (0.39 mm +/-0.05; n = 12) wide. Body ending in a copulatory bursa; ventrolateral and lateroventral rays fused for one-half length from origin in base of bursa; lateral rays with a common stem; externo-dorsal rays bifurcate from base of dorsal ray, forming two lateral lobes. Dorsal ray divided into two branches with each branch terminating in three digitations different in size; spicule equal in size, 0.73–0.96 mm (0.77 mm +/- 0.10; n = 10) (Fig. 3d, e).
Remarks
Adult worms collected from the free-ranging dogs studied here were identified at specific level based on the characteristics of the anterior and posterior ends of the body of both sexes, mainly in the buccal capsule armed with three pairs of ventrolateral teeth, and the dorsal rays of the bifurcated copulatory bursa, features that agree with those presented in the re-description of the species by Burrows (1962) for cats and dogs from USA, and Uppal et al. (2017) for dogs from India. Blastn query of ITS gen results in a similarity of 100% with specimens found in dogs and cats from Australia (KP844730) (Šlapeta et al. 2015) and 100% with cox1 gen with a specimen found in gray fox (Urocyon cinereoargenteus) from Mexico (MZ821647) (Panti-May et al. 2022).
Uncinaria stenocephala (Raillet, 1884) Froelich, 1789
Material: CNHE: 13000. cox 1 GenBank: PP574872, PP574873; 28S GenBank: PP472461
Diagnosis: Based on 38 specimens (twenty females and eighteen males). Buccal capsule distinguished by the presence of a pair of chitinous lateral plates with rounded margins. Females: body 0.7–1.1 mm (0.84 mm +/- 0.110; n = 19) long by 0.26–0.36 mm (0.31mm +/-0.030; n = 7) wide; distance between vulva and anterior end of body 5.01–7.23 mm (5.95 mm +/- 0.98; n = 4), and between anus and tail 0.16–0.23 mm (0.19 mm +/- 0.018; n = 19). Males: body 0.6–0.9 mm (0.78 +/- 0.098; n = 18) long by 0.30–0.25 mm (0.28 +/-0.019; n = 9) wide. Copulatory bursa with semi-ovate lateral lobes; dorsal ray distally forked, each branch ending in three pronged of similar size. Spicules of equal size 0.76–0.68 mm (0.70 mm +/-0.047; n = 13) (Fig. 3f, g).
Remarks
Adult worms collected from the free-ranging dogs studied were identified at a specific level based on the characteristics at the anterior and posterior ends of the body in males and females, traits that agree with those presented in the re-description of the species carried out by Górski et al. (2006) for canids from Poland and Ransom (1924) for dogs, foxes and badgers from USA. The sequence obtained for the 28s gene had 100% similarity compared to larvae of this nematode species (MT343056) by Karadjian (2020) from France. The sequences of cox1 gene generated in our study represent the first for this nematode species.