Natural heavy infection with immature sarcocysts of Sarcocytis spp. in sheep in Mosul city: A case report

1. For the first time, the emergence of large numbers of immature macroscopic cysts in the esophagus in a small age about a year, indicating the widespread of oocysts of Sarcocystis  raised by the final hosts( Cats ) attesting to severe pollution of rangelands.

2. Economic loss resulting from infection , which reduces the value of meat in terms of the appearance of unwanted meat due to the presence of macrocysts , as well as its impact on the quality and quantity of meat.

 3. The necessity of examining the carcasses by the veterinarians in the slaughterhouses, As the presence of macroscopic cysts is not limited to the esophagus only if it can be found in other parts such as the heart and the diaphragm muscle.

 4.The necessity of limiting the presence of cats with animals in the pastures due to their main role in spreading the diseas

Introduction

Sarcosporidiosis that has high prevalence in sheep causes micro and macrocystis (muscular sarcocysts) in skeletal and cardiac muscle related to the final hosts (dogs or cats) respectively. The Sarcocystis protozoan parasite belong to the phylum Apicomplexa, Family Sarcocystidae and the Sarcocystis species follow an obligatory two hosts life cycle, alternating between an intermediate host (prey- sheep) and definitive host (predator - dogs or cats). Both Sarcocystis gigantea and Sarcocystis medusiformis are responsible for developmental of macroscopic cysts in muscles of sheep (1-3). Although the infection of sarcosporidiosis in sheep are not zoonotic but the importance of the infection lies in the carcass condemnation is justified on the basis of the negative visual impact that cysts may have on the consumer (4-7).

Material and methods

Sheep at the first year of age, slaughtered at one of butcher's shop, through the microscopical examination of carcass found large number of small nodules in esophageal muscles were randomly distributed with in the esophageal muscles. The portion of esophagus about 40 cm were resected and transported to lab of parasitology for macroscopic examination sarcosystis of sarcosystis were counted and collected about 30 cysts then measured the cysts by ocular micrometer (8). Cysts were prepared for light microscopically by then fixed in 10% neutral buffered formalin. Processing for histological examination the cysts were embedded in paraffin wax, sectioned at 5 µm and stained with H&E (9).

Result

Macroscopically, the immature macrocysts were detected by gross examination in the muscles of esophagus of sheep. The morphological randomly features of macrocyts were white, rounded or oval cysts heavily distributed throughout esophageal muscles. (Figure 1). Immature sarcocysts were approximately measured 33 µm in length and 25µm in width (Table 1). Histologically, most of sarcocysts appeared to contain only metrocytes (Figure 2).  According to the morphology and size of the cysts as well as microscopical examination most of cysts were immature sarcocysts in the esophagus.

Table 1: The size of immature macrocysts in esophagus of a sheep (n=30 cysts)

Figure 1: Esophagus with heavy infection macrocystes (A), white rounded and oval cysts (B).

Discussion

 Due to difficulty of diagnosing of Sarcosporidiosis in living sheep and the difficulty of examining whole carcass by veterinarians in private butcheries and in our study the only heavy infected sample (esophagus) is difficult to be obtained in other infected muscles.

Most species of Sarcocystis that infect domestic animals are specific species for the intermediate host (10). Sheep are intermediate hosts for the Sarcocystis, Sarcocystis gigantea and Sarcocystis medusiformis, which are transmitted by felids (11). In our study, heavy infected cases with Sarcocystis reveals the fact that large numbers of cats in contact with sheep pastures is considered the main risk factor for infection and supply of raw meat from infected sheep carcasses which contributes significantly to the propagation of Sarcosporidiosis by Sarcocystis (12).

Our study also showed that the infection only with heavy immature macrocysts in young sheep at one year old might probably occurred by either ingested (high dose) of oocysts or sporocysts of Sarcocystis at the same time or at short exposure time with grass contaminated grass with faeces of the infected cats; or due to slow or gradual development of immature macrocysts (13,14) these results confirmed by (15-17) who mentioned that immature Sarcocystis developed in the esophagus and tongue from 1.3 to 4 and 6 months post infection in their experimental study with Sarcocystis gigantea and Sarcocystis medusiformis. Our morphological study revealed that immature cysts vary in shape and size it appears at the round or oval and size ranging from 20-28 x 28-42 µm, this is identical to study done by (14-19).

Figure 2: Immature macrocysts of Sarcocystis spp. contain only metrocystes. H&E, 200x (A), 560x (B).

While our histological study of macrocysts approved that all of macrocysts contain only meterocytes similar to observations by (15) his result revealed that firstly in the cross section of immature cysts contain only metrocytes, while mature cysts containing both metrocytes and merozoites and he added that metrocytes which appeared are closely packed, vesicular cells with definite basophilic nuclei in hematoxylin and eosin stained section, additionally the cyst wall of the immature macrocysts was not measurable at light microscopy of which is important for the differentiation between the species of sarcocysts (10,14,20).

According to (21) the veterinarians working as official meat inspectors at the abattoir, who systematically examined the external surfaces of the carcass, esophagus, heart, diaphragm, peritoneum and pleura to detect macrocysts Sarcocystis species. According to the above-mentioned legislation, partial carcass condemnation when one or more cysts in one organ in this case it is trimmed off. While total execution performed when macrocysts were found in two or more organs (20).

Conclusion

The natural heavy infection with immature macrocysts (Sarcocysts) of Sarcocytis spp. in sheep. Most of the macrocysts (Sarcosysts) were small in size the mean of size between 20- 28×28-42 µm they were histological examination showed that presence of only metrocytes. This confirmed the diagnosis that the sarcocysts were immature macrocysts (sarcocysts) for the Sarcosystis in sheep. It should be the veterinarians working as official meat inspectors at the abattoir, who systematically examined the external surfaces of the carcass, such as esophagus, partial organ condemnation when one or more cysts in one organ in this case it is trimmed off.

Acknowledgments

The authors are very grateful to the University of Mosul/College of veterinary medicine for their provided facilities, which helped to improve the quality of this work.

Conflict of interest

The authors declare that there are no conflicts of interest regarding the publication of this manuscript.