Prevalence of Toxoplasma gondii ‐like oocyst shedding in feral and owned cats in Damascus, Syria

Abstract Background The incidence of toxoplasmosis in humans in Syria indicates an increase in the number of infections with this disease. Cats are the only definitive host of Toxoplasma gondii and excrete environmentally resistant oocysts in their feces. Objectives Estimate the prevalence of T. gondii‐like oocyst shedding in the cat population in Damascus, Syria. Animals One‐hundred domestic cats. Methods One‐hundred fecal samples from cats (68 feral cats and 32 owned cats) were collected in Damascus between October and December 2017 and examined for T. gondii‐like oocysts by direct microscopic examination using Sheather's sugar flotation procedure. Results Examination of the samples showed that 36% (36/100) of the cats were shedding T. gondii‐like oocysts. Sporulated or unsporulated oocysts morphologically consistent with T. gondii were detected in 38.2% (26/68) of the samples collected from feral cats and in 31.3% (10/32) of the samples collected from client‐owned cats. Conclusion The clinical importance of Toxoplasmosis in humans lies in the transmission of Toxoplasma to the fetus especially in the first trimester, resulting in severe clinical symptoms in the infant and leading to spontaneous abortion, stillbirth or other serious health problems and severe sequelae (e.g., mental retardation, blindness, hearing, and neurological disorders). Our results showed higher prevalence in Syria than in Lebanon. High amounts of T. gondii‐like oocyst shedding were detected in both feral and client‐owned cats in Damascus, emphasizing the importance of further research to understand T. gondii infection in people and animals in this region.


| INTRODUCTION
Toxoplasmosis is a zoonotic disease caused by Toxoplasma gondii. 1 Toxoplasma gondii is an obligate intracellular parasitic protozoan with a worldwide distribution, 2 and is an apicomplexan protozoan parasite that infects birds and mammals, including humans. Although infections often are asymptomatic, T. gondii can cause serious disease and death in humans and animals. 3,4 Toxoplasmosis is widespread, and present in every country.
Latent infection with T. gondii is among the most prevalent of human infections. It is estimated that one-third of the world's human population is infected with this parasite. Seropositivity rates range from <10% to >90% in human populations in different areas of the world, which varies with cultural and eating habits. 5 Studies of toxoplasmosis in humans in Damascus, Syria indicate that there has been an increase in the incidence of this disease, with incidence ranging between 30% and 89.7%. [6][7][8] Transmission of toxoplasmosis to humans occurs by eating raw meat containing cysts of Toxoplasma, through food or water contaminated with oocysts excreted by cats, 9 or congenitally via transplacental transmission (congenital toxoplasmosis). If transmission of the parasites to the fetus occurs in the first trimester, it results in the most severe clinical symptoms in the infant leading to spontaneous abortion, stillbirth or other serious health problems and severe sequelae (eg, mental retardation, blindness, hearing, and neurological disorders). 10 In addition, infection with T. gondii is increasingly being recognized as a problem in non-pregnant, immunocompetent adults, where acute infection may lead to impaired eyesight. 11 Cats are reservoirs for several parasites, some of which are responsible for serious zoonotic diseases. They are the only definitive host of T. gondii and excrete environmentally-resistant oocysts in their feces. 12 Therefore, a high risk of Toxoplasma infection exists in humans living in cities with high densities of feral and owned cats. 13 Cats begin to shed oocysts as early as 3 to 8 days after being fed tissue containing cysts. However, oocysts are less infectious and pathogenic to cats than to intermediate hosts. 14 Ingesting oocysts in water, soil or feed is probably the most common route for T. gondii infection in non-carnivorous mammals and birds. Seroprevalence of T. gondii can be high in meat-producing animals around the world (up to 100%), but infection is more common in certain livestock species including sheep and goats. 15 Interest in detecting T. gondii oocysts in the environment is emerging because of recent outbreaks of waterborne toxoplasmosis in humans. Oocysts can survive various inactivation procedures especially those using chemical reagents, 16 and remain viable in water even after exposure to aqueous 2% sulfuric acid for at least 18 months at 4 C. They also resist detergents or disinfectant solutions such as sodium hypochlorite. Drinking water treatment plants using chlorination as the sole method of disinfection could therefore supply water containing infective oocysts. 17 In humans, the percentage of infections caused by oocysts remains undetermined. 18 Toxoplasma gondii infection seems strongly associated with soil contact, 19 contributing up to 17% of infections among pregnant women in Europe, 18 which emphasizes the key role of the environment as a source of infection. Oocysts also can be transmitted to humans by eating contaminated vegetables. A study in Italy showed that in ready-to-eat packaged salads, microscopic examination detected T. gondii-like oocysts in 0.8% of samples, with numbers of oocysts ranging from 62 to 554/g of vegetables. 20 We aimed to estimate the prevalence of T. gondii-like oocyst shedding in the feral and owned cat population in Damascus, Syria.

| Statistical analysis
Statistical analysis was performed using the SPSS 24 program, and the Chi-squared test was used to assess differences in the prevalence of T. gondii-like oocyst shedding in feral and owned cats. P < .05 was considered statistically significant.

| RESULTS
Feces of 100 cats were examined by microscopy for detection of T. gondii-like oocysts to assess oocyst shedding. Thirty-six percent (36/100) of the samples contained T. gondii-like oocysts, with feral cats showing higher levels of shedding than owned cats as shown in Table 1.
The difference in shedding prevalence between feral cats (38.25%; 26/68) and owned domestic cats (31.2%; 10/32) was not significant (P = .66). The ingestion of unfiltered water contaminated with T. gondii oocysts has been linked to toxoplasmosis. 23 Thus, drinking water is increasingly being investigated as a risk factor, and has been found to be an important source of infection in tropical and subtropical countries, where surface water may be used for human consumption without any purification. 24 Unwashed vegetables and fruits, or washing with contaminated water, also could increase risk of T. gondii infection. In addition, the role of water that may contain infective Toxoplasma oocysts and thereby contaminate fruit or vegetables during growth is important, as previously shown. 25 Our aim was to determine the prevalence of oocyst shedding in Therefore, future studies must include more samples from other cities.

| DISCUSSION
Toxoplasma gondii oocyst genera could not be differentiated in our study because PCR was not available at the microbiology laboratory in which the experiments were conducted.
Hence, future research on the seroprevalence of toxoplasmosis in cats living in Damascus are recommended to understand infection with T. gondii in feral and domestic cats, and assess its correlation with seroprevalence in humans.

ACKNOWLEDGMENT
No funding was received for this study.

CONFLICT OF INTEREST DECLARATION
Authors declare no conflict of interest.

OFF-LABEL ANTIMICROBIAL DECLARATION
Authors declare no off-label use of antimicrobials.

INSTITUTIONAL ANIMAL CARE AND USE COMMITTEE (IACUC) OR OTHER APPROVAL DECLARATION
Authors declare no IACUC or other approval was needed.

HUMAN ETHICS APPROVAL DECLARATION
Authors declare human ethics approval was not needed for this study.