Toxocariasis: The Sanitary Hazard in Urban Communities of Iran

Toxocariasis is human infection caused by larval stage of Toxocara helminthes. The adult Toxocara helminthes live in intestine of dog and cat, but if the human accidentally ingests the egg, the larva is released into the intestine and then penetrating to mucosal capillaries and by blood stream migrates to various organs. Considering to the larva of parasite cannot be adult in human body and finally is destroyed, but its placement in the organs leads to irritation and inflammation of the tissue and appearance of signs and symptoms. The parasite affects liver, lung and central nervous system more than other organs. The most obvious symptoms of this disease are irregular fever, liver enlargement and sever eosinophilia. Other symptoms depend on the final location of the parasite, for example, respiratory symptoms (similar to asthma) will occur at the time of parasite settling in the lung and nervous disorder when the parasite is deployed in the nervous system (1). Sever clinical symptoms due to the disease is more common in 2 to 7 years old children, because of contacting with polluted playground soil or stray dog and cat, that the chance of them getting disease is increased (2). In developing countries including Iran, the diagnosis of the disease is done by collecting signs and symptoms, evaluating risk factor and laboratory results. Laboratory results which is considered on this disease containing eosinophilia, hypergammaglobulinemia and increasing of isohemagglutinin A and B. The serological test by ELISA technique was used for diagnosis of anti-parasite antibody in European countries and USA, the sensitivity and specificity of this test was 78 and 98%, respectively. There is no definitive guideline to the treatment of the disease but the most common treatment plan is 400 mg albendazole and 100 to 200 mg mebendazole, twice a day for 5 days (1).
In recent years the number of dogs and cats in the human environment has been increased in our country and consequently the rate of soil contamination to eggs of Toxocara has been increased. The consequence of this phenomenon is an increasing chance of human contact the egg of this parasite and onset of toxocariasis. The studies in Iran is reported the rate of soil contamination to this parasite is minimum 3.9% (Urmia) to maximum 63.3% (Khoramabad), while the rate of contamination in soil of Arak parks is 26.6% (3-5). In addition, the results of serological study showed that the prevalence of toxocariasis in 5 to 15 years old asthmatic patients was 1.8%, in Arak (6). But the results of a review study showed that the prevalence of toxocariasis in general population of Iran was 15.8% and this rate is increasing (7).
Changes in Ecosystem and abundance of garbage in Iranian cities have led to overabundance of dogs and cats in human environment. On the other hand, accepting some of cultural western lifestyle such as keeping pets, apart from their social and legal responsibility has been caused increasing risk of infectious disease transmitted by animals such as toxocariasis.
Due to the relatively high prevalence of Toxocara infection among dogs and cats in Iran, the need to pay attention to the disease caused by this parasite is felt as a potential medical and health hazard in the country. In this condition, holding workshops for remembering of symptoms, diagnosis method, treatment and prevention of the disease for clinician associate with infected patients, would has an important role for quick diagnosis and remedy of the patients and would reduce the corporal and psychological load of them. Also, performing the research studies would help to know current epidemiological situation and changes that have taken place in various parts of Iran. In the other side, encouraging scholars for isolation, purification and examine excretory-secretory antigens of this parasite that used for producing the serological diagnostic kits could increase accuracy and reduce cost of diagnosis test of disease and finally improve the level of health in community.