[Studies on thelaziasis of cattle. I. Thelazia skrjabini Erschow, 1928 found in Japan]

Diversity of Thelazia spp. in domestic cattle from Romania: epidemiology and molecular diagnosis by a novel multiplex PCR

BACKGROUND

Thelaziosis is a neglected vector-borne disease caused by parasitic nematode worms of the genus Thelazia which affects various hosts. Limited attention has been given to ungulate-associated Thelazia species. Current diagnosis of thelaziosis and the identification/differentiation of species heavily relies on morphological features. Therefore, we conducted an epidemiological study in Romanian cattle, with the aim to obtain morphological and molecular data that can be used for species identification.

METHODS

The eyes of 705 slaughtered cattle were sampled and subjected to morphological identification, morphometric analysis, and molecular characterization. PCR amplification and sequence analysis were performed based on the cytochromec oxidase subunit 1 (COI) gene. Statistical tests assessed the correlations between infection parameters and ecological or biogeographical factors. A novel PCR method was developed based on the consensus sequence from each species. Specific forward primers were designed for each of the three species, and a reverse primer (COIintR) was used for all reactions. A consensus thermal profile was established by gradient PCR amplification of each species separately.

RESULTS

Of the sampled cattle, 19.3% were infected with Thelazia spp. Prevalence varied significantly with ecogeographical factors. A total of 585 Thelazia nematodes were recovered, with T. rhodesi being the most abundant, followed by T. skrjabini and T. gulosa. Morphometric and molecular analyses supported the morphological identification, yielding unique sequences for each species. From the 59 T. rhodesi specimens sequenced, 29 unique sequences were obtained, with a 99.1-99.85% nucleotide identity to the only other COI sequence present in GenBank®. All nine T. gulosa isolates were unique (99.37-100% nucleotide identity to other sequences), while T. skrjabini specimens displayed 98.47-100% nucleotide identity to the sole available sequence.

CONCLUSIONS

Bovine thelaziosis is prevalent in Romania, raising concerns for animal welfare and potential economic impacts. Infected cattle grazing alongside vulnerable wild ruminants, such as the European bison, may affect conservation efforts. Our newly developed multiplex PCR shows promise as a valuable surveillance tool, enabling the detection of occult infections in apparently healthy animals through lachrymal secretion testing.

Morphological differentiation among three Thelazia species (Nematoda: Thelaziidae) by scanning electron microscopy

Thelaziasis is an ocular infection of several mammals caused by nematodes of the genus Thelazia (Spirurida, Thelaziidae). The adults live in the lachrymal ducts and conjunctival sacs of infected animals, and transmission occurs by means of different species of muscids. T. rhodesi, T. skrjabini, and T. gulosa affect mainly cattle, inducing conjunctivitis, keratitis, and ocular discharge. This article describes the morphological features of adult T. rhodesi, T. skrjabini, and T. gulosa by scanning electron microscopy and highlights the most relevant differences for their identification.

Thelazia rhodesi (Spirurida, Thelaziidae), bovine eyeworm: morphological study by scanning electron microscopy

Thelazia rhodesi (Spirurida, Thelaziidae) is a parasite of ruminants, which causes ocular infections. Scanning electron microscopy was used to study the surface ultrastructure of adult worms of this nematode. At the anterior end of both sexes, the buccal opening was orbicular. Around the mouth, four pairs of cephalic papillae and two lateral amphids were seen. A pair of lateral cervical papillae was present. In the female, the vulva was located at the anterior part of the body, and the tail end was stumpy with two phasmids near its extremity. In the male, the tail was blunt, without caudal alae, and curved ventrally. There were 14 paired preanal papillae, one single papilla directly anterior to cloaca, one paired postanal papilla, and two phasmids at the posterior end. The spicules were unequal and dissimilar. The cuticle was transversally striated and appeared serrated.

Fine structure of body surface of Thelazia skrjabini (Nematoda: Spirurida, Thelaziidae)

Thelazia skrjabini (Spirurida, Thelaziidae) is a parasite of cattle that causes ocular infections. Scanning electron microscopy was used to study the surface ultrastructure of adult worms of this nematode. At the anterior end of both sexes, the buccal opening was orbicular. Around the mouth, two circles of cephalic papillae were seen: the inner circle with six papillae and the outer circle with four submedian papillae. At both lateral sides of the head, two amphids were observed. A pair of lateral cervical papillae was present. In the female, the vulva was located at the anterior part of the body and the tail carried an anal pore and two phasmids near the tip. In the male, the tail was blunt without caudal alae and curved ventrally. There were 31 to 38 unpaired preanal papillae, two paired postanal papillae, and two phasmids at the posterior end. The cuticle had fine, scarcely visible transversally striations. At the anterior end of the two cases, one abnormal mass was seen.

First report of Thelazia sp. from a captive Oriental white stork (Ciconia boyciana) in Japan

Nematodes of the genus Thelazia were recovered from the cornea and inferior conjunctival sac of an immature Oriental white stork (Ciconia boyciana). The bird hatched and reared at the Toyooka Oriental White Stork Breeding Center, Hyogo Prefecture, Japan, but died of chlamydiosis. There were neither gross nor histopathologic ophthalmic lesions. The eye worm from a bird is believed to be first reported in Japan. As regarding reintroduction plan for the Oriental white stork, control measures for prevent further infection with the eye worm will be needed.