Clinical manifestation and epidemiological findings of human linguatula serrate infection in Iran: systematic review

Phylogenetic, molecular, and microscopic investigation of Linguatula serrata infection in stray and road-killed dogs in Northwest Iran

BACKGROUND

Linguatula serrata is a cosmopolitan zoonotic parasite. Canids serve as definitive hosts, while herbivores acts as intermediate hosts. Adult L. serrata are found in the nasal and respiratory passages, whereas the immature stages are located in the mesenteric lymph nodes, liver, spleen, lungs, and, occasionally in other organs. Humans can serve as intermediate hosts, with visceral infections, or as definitive hosts with nasopharyngeal infections. This study aimed to investigate the infection rate of stray and road-killed dogs with L. serrata and to explore its phylogeny.

MATERIAL AND METHODS

A total of 150 stray dogs and 100 road-killed dogs were examined for L. serrata eggs in feces and nasal secretions using microscopy and molecular tests, and for adult L. serrata through necropsy.

RESULTS

The results showed that 174 of 250 (69.6%) studied dogs were positive for L. serrata by at least one of the examination methods. The prevalence in road-killed and stray dogs was determined to be 72% and 68%, respectively. The L. serrata infection rate based on fecal microscopy in the road-killed and stray dogs was 29% and 46.7%, respectively, and by fecal PCR was 59% and 48.7%, respectively. The rate of infection with L. serrata based on nasal secretions in road-killed and stray dogs was 14% and 26%, respectively, using microscopy, and 44% and 43.3%, respectively, using PCR. In the road-killed dogs, based on necropsy, 46% were positive. The results of this study show that PCR is more effective than microscopy for detecting L. serrata infections in dogs. PCR amplicon of the expected size for Linguatula of approximately 595 bp for 18S rRNA were generated from the L. serrata isolates using described specific primers.

CONCLUSION

It can be concluded that the rate of infection in dogs and possibly other carnivores, herbivores, and man, is high in this locality; hence, strict control measures should be conducted to overcome the risk of infection with this zoonotic disease.

Unusual parasitoses in urban dogs: Urinary capillariosis and linguatulosis, cases report

Parasitic diseases caused by uncommonly diagnosed parasites may pose a threat to companion animals' health in urban environments where they are least expected. The pentastomid Linguatula serrata (tongue worm) and the capillarid Pearsonema plica (syn. Capillaria plica) are parasites with an indirect life cycle, infecting both domestic and wild carnivores. The present report describes two cases: the first one of urinary capillariosis and the other of linguatulosis, in two dogs living in the urban environment of Athens, Greece. In the case of capillariosis, the dog never lived out of the city, so it was presumably infected in the urban environment. On the contrary, in the case of linguatulosis, the dog was adopted at a young age from a rural environment but remained asymptomatic for several months while living in the city. Both dogs had mild symptoms, compatible with these infections. Urinary capillariosis and linguatulosis are uncommon in owned, pet dogs, living in cities due to epizootiological characteristics, i.e. need for wildlife reservoir for P. plica and consumption of raw infected viscera for L. serrata. Different factors contribute to the fact that such infections may occur in scenarios where they are least expected. Recent studies show a progressive worldwide increase in the number of uncommon parasitoses in pet animals, that in some cases, such as linguatulosis, are of zoonotic relevance. Regular parasitological examinations and preventive antiparasitic schemes are necessary in order to treat and prevent infections in pet animals and safeguard the health of both animals and humans under the concept of One Health.

Global status of neglected human Linguatula infection: a systematic review of published case reports

Human linguatulosis is a rare but highly specialized pentastomid parasitic infection all around the world. The disease is caused by worm-like parasites which share some morphologic features of arthropods and annelids. The life cycle of Linguatula spp. is provided as an example of pentastomid biology. The adult forms of Linguatula spp. are found in the nasal passages and frontal sinuses of dogs and other canids, domestic animals, and humans. Infestation may occur in the viscera, where immature forms develop in the liver, spleen, lungs, eyes, and other organs, or in the nasopharyngeal area. This review includes previous studies on the genus Linguatula in Iran and other countries from 1940 to 2019. Considering a few reports of human infestation, a comprehensive search was performed on both English and Persian databases for publications reporting human cases all around the world. Finally, 30 papers of 62 human cases were included in this study. The mean age of the patients was 25.8 years (varied from 8 to 79 years). Altogether, 41 (66.1%) and 21 (33.9%) of the patients were female and male respectively. The maximum cases (n = 25) were from Sudan. Nasopharynx was the most frequently involved organ in human cases. Our findings offer that physicians should consider the Linguatula infection in patients with complaints like unexpected dysphagia, with coughing, sneezing, and vomiting, after consuming raw/undercooked contaminated ruminant's viscera.