Introduction
Rodents with about 2280 species are the largest species of mammal on earth that can live in different geographical areas and climates. Eight families and 69 species of rodents have been identified in Iran so far. These organisms with the ability to transmit about 200 diseases to humans and other animals are the source of great economic and health damage [1].
The importance of gastrointestinal metazone parasites in rodents can be examined from several aspects. Rodents are crucial reservoirs and resources for several diseases between humans and animals and have a vital role in the transmission and spread of infectious diseases [2]. Various species of nematodes, cestodes, and trematodes live in the gastrointestinal tract, respiratory tract, bladder, and peritoneal area of ​​rodents. So far, 13 species of parasitic worms have been transmitted from rodents to humans, the most crucial of which are rat oxyure, Hymenolepis nana, Hymenolepis diminuta, and Echinococcus multilocularis [3, 4].
Many parasites exist in rodents, some of which are zoonoses and can be transmitted to humans. The high prevalence of rodents, especially in human areas, causes the transmission of these parasitic agents to humans. Among rodent worms, gongylonema worms are transmitted by stool-eating beetles [5]. 
The high abundance of these beetles in Tabriz City has caused a high diversity of gongylonema species in this region. Therefore, this study was conducted to identify gongylonema parasites and their zoonotic importance in rats of Tabriz City.
Materials and Methods
In this study, 100 rats (29 Rattus rattus and 71 Rattus norvegicus, 32 male and 68 female, in the age range of 1-3 years) from different areas of Tabriz City were caught with a live trap. The bait used in this study was bread soaked in oil or cucumber. The traps were collected the day after installation and transferred to the parasitology laboratory affiliated with the Faculty of Veterinary Medicine of the Islamic Azad University, Tabriz Branch. There, the rats were first identified and then necropsied. In this study, to determine rats, head and body size (from the tip of the nose to the base of the tail), tail (from the base of the tail to the end of the tail along the vertebrae without end hairs), hind legs (from the back of the heel to the tip of the longest toe without Nails), ears (from the top edge of the ear to the tip of the earlobe) were measured.
The rodent was killed by cotton soaked in ether or chloroform and placed in a necropsy tray and the method of killing in rats was by animal ethics. Necropsy was then fixed to the ionolyte floor with round bottom needles and necropsied. To isolate the parasites of the genus Gongylonema, the esophagus and gastric mucus were carefully examined and if the parasite was observed, they were completely isolated. Eventually, the parasites settled on the slide and were clarified with lactophenol. Azocarmine was also used for staining [6, 7].
After confirming the final diagnosis of Gongylonema species, the parasites were photographed. The required parts were also removed using a previously calibrated microscope.
Results
In this study, 100 rats were caught and examined for the diversity of Gongylonema parasites and the morphology of these parasites.
The only Gongylonema species isolated from esophageal and gastric tissues in this study was Gongylonema neoplasticum.
Gongylonema neoplasticum: A nematode of the spiruridae family that is a parasite of the stomach and esophagus of black and brown Rattus. The skin plaques of the anterior region are symmetrical (Figures 1, 2, 3).

In this study, isolated parasites were isolated and it was found that the length of males was 7-18 mm. The unequal spicules were also 100 and 550 microns in length. Female worms are 40 to 75 mm long. Also, the female worm vulva was located near the posterior end [7]. In this study, 2 cases of this parasite were isolated from esophagus and gastric mucus of Rattus. In a study conducted by Eberhard et al., the parasite was reported in Africa, Asia, Australia, and Central America [4].
Discussion and Conclusion
The study of rodent gastrointestinal parasites is of medical, veterinary, and biological importance. Rodents are important reservoirs of infectious diseases and important foci of diseases transmitted by them are scattered and observed in different parts of Iran [8, 9, 10, 11, 12].
In this study, Gongylonema neoplasticum from Rattus esophagus and stomach was reported for the first time in Tabriz City in northwestern Iran.
Finally, it should be noted that the presence of stool-eating beetles in some study areas can threaten the health of people in these areas [13].
Therefore, parasites of the spiruridae family can be considered in terms of health, and if neglected, they can cause infection and secondary complications in humans and animals [9, 10].
Gongylonema neoplasticum is transmitted to humans by dung beetles. This parasite is located in the human body in the esophagus, gums, lips, and pharynx and causes inflammation and swelling of the infected tissues, and these patients suffer from the feeling of an object moving in the neck and upper parts of the digestive system.
Despite the diversity in the number and species of rodent populations in different climates of Iran, the importance of such animals in terms of health compared to other animal species have received less attention [11, 14, 15]. Due to the climatic diversity in Iran, the study of rodent parasitic fauna is of particular importance in determining the distribution of parasites and their epidemiological study to control and prevent diseases transmitted by rodents. Also due to the increasing population of rats near human settlements and the contamination of these rats with different types of zoonotic parasites, more parasitological studies should be conducted in different geographical regions of Iran and other countries.

Ethical Considerations
Compliance with ethical guidelines
This article was approved by the Research Council of the Islamic Azad University of Tabriz with ethical code IR.IAU.TABRIZ.REC.1400.206.

Funding
This article was extracted from the professional doctoral dissertation of Sahand Fattahi, Department of Parasitology, Faculty of Veterinary Medicine, Tabriz Medical Sciences Branch, Islamic Azad University, Tabriz, Iran.

Authors' contributions
Writing and editing of the manuscript: Yagoob Garedaghi; Data collection and statistical analysis: Sahand Fattahi. 

Conflicts of interest
The authors declared no conflict of interest.

Acknowledgements
Appreciate and thank the support of the Vice Chancellor for Research, Islamic Azad University, Tabriz Branch.


References