Prevalence of Linguatula serrata nymphs and gross changes of infected mesenteric lymph nodes in sheep in Urmia, Iran

In an abattoir survey, the infection rate to the nymph of Linguatula serrata in 1333 mesenteric lymph nodes collected from 200 native sheep was investigated in North West of Iran. The lymph nodes were categorized based on their gross appearance (color and consistency). The results indicated that 105 (52.5%) out of 200 animals were infected with nymphal stage of L. serrata. Two hundred and eighty-eight (21.6%) mesenteric lymph nodes had the parasite's nymphs. The results revealed that the infection rate to the nymphs of parasite in hemorrhagic (78.0%) and black-colored (86.3%) nymph nodes were significantly (P < 0.05) higher than the infection rate in normal-colored nodes (9.3%). The difference between infection rate of hemorrhagic and black-colored lymph nodes was non-significant (P > 0.05). When compared based on consistency, the results showed that in soft lymph nodes (99.0%) the infection rate was significantly (P < 0.05) more than that in normal (14.6%) and hard (33.3%) lymph nodes. In addition, the hard lymph nodes were significantly (P < 0.05) more infected than normal ones. Based on lymph node color, the intensity of infection (mean number of nymphs ± standard error) in normal, hemorrhagic and black nods was 2.67 ± 0.29, 10.81 ± 1.19 and 12.02 ± 1.34, respectively. The mean number of parasites in hemorrhagic and black-colored lymph nodes were significantly (P < 0.0005) more than mean number of parasites in normal-colored nodes. Based on lymph node consistency, intensity of infection in normal, soft and black lymph nodes was 3.84 ± 0.34, 16.64 ± 1.41 and 4.11 ± 1.22, respectively. When compared based on lymph nodes consistency, the soft lymph nodes was significantly (P < 0.0005) more severely infected than normal and hard ones. Our results indicated a high rate of infection of lymph nodes in sheep in this region of Iran. Due to consumption of raw or under-cooked liver and visceral organs of sheep by human of this region, the importance of inspection at slaughter needs to be emphasized.