Role of Intermediate Hosts' Lymph Nodes in the Continuity of Life Cycle and Prevalence of the Linguatula Serrata Parasite

Linguatula Serrata is a zoonotic parasite. Several cases of human infection have been reported from Iran and other countries. Sheep and Canids, as the intermediate and definitive hosts, respectively, play an important role in the persistence of infection in humans. The present study aimed to evaluate the lymph node infection in the sheep with respect to host factors (age and gender), lymph nodes (color and consistency), and their role in the infection of various hosts.

This cross-sectional study included the randomly selected samples of mesenteric lymph nodes from slaughtered sheep (n=619) of different areas of Ilam province, Iran, from April to November 2015. The positive samples were determined by collecting Linguatula Serrata nymphs. Following that, the obtained data were analyzed using statistical tests.

Out of 619 sheep samples, 99 (16%) samples were infected with Linguatula Serrata nymphs. The highest prevalence rates were observed in the southern areas, including Abdanan, Darreh Shahr, and Dehloran (19%). On the other hand, the lowest prevalence rates were in the eastern regions, including Shirvan, Sirvan, and Chardavol (11.7%). The infection prevalence rate in females was 25.6% (n=52 of 203) that was more than that in males (11.3%; n=47 of 416). There was a significant relationship among gender, age, and the prevalence rate of the infection (P<0.05). The highest and lowest infection rates were observed in the age groups of ≥3 (23.4%) and <1 (11.3%), respectively.  Furthermore, the maximum infection rates were noted in the dark and soft lymph ‌‌nodes, (54.3% and 38.7%, respectively), compared to normal ones (11.5%, and 10.4%, respectively). The color and consistency of the lymph nodes showed a significant relationship with the infection rate (P<0.05).

Considering the high levels of infection in sheep, which is a reflection of dogs' infection in the area and the potential risk to humans, health education and observance of the principles of prevention, especially avoiding the use of infected lymph nodes to feed dogs, are essential to reduce the parasite infection in the hosts.