Document Type : Research Paper
Author
Department of Food Hygiene and Aquatic, Faculty of Veterinary Medicine, University of Tabriz, Iran
Abstract
Keywords
Main Subjects
Extended Abstract
Introduction
Linguatula serrata is a zoonotic pentastomid parasite whose adult form inhabits the upper respiratory tract of definitive hosts, primarily canids. The parasite’s eggs are excreted through nasal discharge or feces and may be ingested by intermediate hosts such as small ruminants. After ingestion, the larvae hatch in the gastrointestinal tract, penetrate the intestinal wall, and migrate to organs including the liver, lungs, spleen, and especially the mesenteric lymph nodes. The nymphal stage remains in these tissues until consumed by a definitive host, thereby completing the parasite’s life cycle. Infected ruminants usually show no clinical symptoms, and the infestation is often detected during post-mortem inspection at abattoirs. However, in cases of heavy infestation, signs such as general weakness, weight loss, and mesenteric lymphadenopathy may occur. In humans, the infestation can result from ingestion of either parasite eggs or raw/undercooked infected organs (e.g., liver, lungs), leading to visceral linguatulosis or nasopharyngeal syndrome (Halzoun), respectively. Symptoms in humans vary and may include allergic reactions, fever, abdominal pain, nasal irritation, sneezing, pharyngitis, and coughing. Given the zoonotic importance of this parasite and the typically asymptomatic nature of infestation in livestock, slaughterhouses play a crucial role in identifying and monitoring infestations. Numerous studies from Iran and other countries have reported variable prevalence rates of L. serrata infection among livestock, highlighting the persistent presence of the parasite’s life cycle, especially in rural and semi-industrial settings. This study aimed to determine the prevalence of L. serrata infestation in the mesenteric lymph nodes of slaughtered sheep and goats in Tabriz, Iran, during the 2023–2024 period, and to evaluate its association with animal species, sex, age, and season.
Materials and Methods
A cross-sectional study was conducted over one year (April 2023 to April 2024) at the Tabriz industrial abattoir, located in East Azerbaijan province, Iran. Sample size was calculated using a standard epidemiological formula:
n = Z²·P(1−P)/d², where Z is the z-score corresponding to 95% confidence (1.96), P is the expected prevalence (0.5), and d is the desired precision (0.05). Based on this, 384 animals per species were required. To enhance accuracy, 400 sheep and 400 goats were randomly selected. From each animal, five mesenteric lymph nodes were collected, yielding a total of 4000 nodes. The animals were chosen randomly across different seasons, and data on age (classified into <2 years, 2–3 years, >3 years) and sex were recorded. Lymph nodes were dissected and placed in warm water to allow nymphs to emerge. Morphological identification was based on features such as tongue-like shape, segmented body, and characteristic spines. Collected data were analyzed using SPSS version 26. Descriptive statistics were used to calculate prevalence by species, sex, age group, and season. Differences between groups were tested using the Chi-square test, with statistical significance set at p < 0.05.
Results
Out of 800 animals examined, 118 (14.8%) were infested with L. serrata nymphs. Of the 4000 lymph nodes inspected, 354 (8.85%) were positive, with 265 (6.6%) from goats and 80 (2%) from sheep. The infestation rate was significantly higher in goats (19.3%) than in sheep (10.3%) (p < 0.05). Female animals had significantly higher infestation rates than males: in sheep, 17.5% of females vs. 5.7% of males were infested; in goats, 44.1% of females vs. 7.7% of males were positive (p = 0.000). Age-related trends showed increased prevalence with age. In sheep, the highest infestation was observed in animals over 3 years (12.6%), and the lowest in animals under 2 years (0%), though the difference was not statistically significant (p = 0.09). In goats, the age-related difference was significant (p = 0.009): 24.9% in those over 3 years, 17.4% in the 2–3 year group, and 7.8% in animals younger than 2 years.
Seasonal analysis revealed significantly higher infestation rates during the colder months. In sheep, the highest rate occurred in autumn (18.5%), while the lowest was recorded in spring (5.5%) (p = 0.041). A similar pattern was observed in goats: 29% in autumn, 21% in winter, and reduced rates of 15% and 12% in spring and summer, respectively (p = 0.013).
Conclusion
This study highlights a relatively high prevalence of L. serrata nymphal infestation in the mesenteric lymph nodes of slaughtered goats and sheep in Tabriz, with significantly higher infestation rates observed in goats compared to sheep. Female and older animals were more frequently affected, suggesting a cumulative exposure risk over time. Furthermore, the increased prevalence during colder seasons implies a possible seasonal pattern in parasite transmission or host susceptibility. Given the zoonotic potential of L. serrata and the absence of obvious clinical signs in infested livestock, routine meat inspection, particularly of mesenteric lymph nodes, remains essential for early detection and monitoring. These findings underscore the importance of continued surveillance at the abattoir level and support the implementation of targeted control strategies, including improved waste management, reduced exposure of dogs to infested offal, and enhanced awareness among farmers and slaughterhouse workers. Future studies should focus on molecular identification and strain differentiation, as well as broader geographic surveillance to better understand the epidemiology of L. serrata in Iran.
This article contains all the data that were created or evaluated during the research.
The authors would like to sincerely thank the members of the Faculty of Animal Sciences, University of Tehran Research Council for the approval and support of this research.
The author declares no conflict of interest.
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