Eosinophils and Parasitic Infections

1Department of Parasitology and Mycology, School of Medicine, Baqiyatallah University of Medical Sciences, Tehran, Iran 2Health Research Center, Life Style Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran 3Research Center of Pediatric infectious Diseases, Institute of Immunology and Infectious Diseases, Iran University of Medical Sciences, Tehran, Iran Int J Enteric Pathog. 2018 November;6(4):108-112


Background
Eosinophils, a group of white blood cells (WBCs) in human and some other animals, were discovered by Paul Ehrlich using eosin dye. 1 The normal percentage of eosinophils in the peripheral blood is 3%-5% and the increase of these types of granulocytes known as "eosinophilia" happens when absolute eosinophil count exceeds the normal range (350-500/mm 3 ). 2,3ypereosinophilia is observed either due to the clonal expansion of eosinophils via a somatic mutation or in response to the secretion of exogenous type 2 cytokines such as interleukin-3 (IL-3), interleukin-5 (IL-5), and granulocyte-macrophage colony-stimulating factor (GMCSF). 4 Some new studies have proposed the contribution of eosinophils in the pathogenesis of various diseases.][7][8] Eosinophils dysregulate immune responses related to allergic diseases, such as asthma.Furthermore, this group of immune cells is often conceptualized as destructive end-stage effector mainly related to parasitic diseases especially helminthic infections such as intestinal and tissue nematode infections. 6,7][18] To the best of our knowledge, the level of eosinophils in different parasitic diseases less has been evaluated, particularly in Iran.Therefore, the aim of the present study was to evaluate and compare the percentage of eosinophils in different parasitic diseases at Baqiyatallah hospital, Tehran, Iran.

Materials and Methods
In this cross-sectional study, the samples from 172 patients including 74 cases suffering from helminthic infections and 98 cases with protozoan diseases were evaluated.The samples from the patients who had other types of diseases were excluded.Moreover, in order to attain more accurate results, only one parasite was considered.WBC count and levels of eosinophils were assessed for all 172 cases.Helminthic infections included fasciolosis, hydatidosis, hymenolepiasis, taeniasis, ascariasis, enterobiasis, trichostrongyliasis, hookworm infection, and strongyloidiasis, amoebiasis, giardiasis, toxoplasmosis, blastocystosis and malaria, cutaneous and visceral leishmaniasis were among the protozoan infections (the number of samples is shown in Table 1).
Most of the samples were obtained from the patients referred to the laboratory of Baqiyatallah Hospital, whereas some of the fascioliasis, hydatidosis, trichostrongyliasis, strongyloidiasis, leishmaniasis and malaria samples were obtained from the patients referred to Tehran University of Medical Sciences (Tehran, Iran), Pasteur Institute (Tehran, Iran), and two private medical laboratories in Lahijan and Amol, Iran.
The samples were prepared by direct wet mount and formalin ether concentration for the diagnosis of the intestinal parasites, scotch tape test for the diagnosis of Enterobius vermicularis, and serologic tests for the assessment of tissue parasites including Fasciola spp., Echinococcus granulosus, and Toxoplasma gondii.
Eosinophils were counted by Sysmex KX-21 automated hematology analyzer (Japan) and rechecked manually.Eosinophils with the counts of 6% or more were considered as eosinophilia. 2,3

Discussion
[11][12][13][14][15][16][17][18]  Fasciolosis is one of the most common zoonotic infections in Iran and in some parts of the world.The largest epidemic of fasciolosis occurred in north of Iran (Guilan) during two previous decades and an emerging infection was also observed in Kermanshah, Iran. 19,20In the present study, in 72.2% of 18 patients infected with Fasciola spp., the percentage of eosinophils was greater than or equal to 6%.Karahocagil et al detected 24 patients with fasciolosis from 92 individuals with a history of watercress ingestion.Eosinophilia was observed in 17 persons (70.8%), which is similar to our results but the average percentage of eosinophils was 30.8±25.7, 10 whereas mean eosinophil count was 7.6% (6%-14%) in our study.The eosinophilia was seen in 19/20 (95%) of the patients suffering from fasciolosis in a hospital in Spain. 21In another study in our country, eosinophilia greater than 30% was reported in Guilan (75%) and Kermanshah (42%). 19Considering the fact that fasciolosis is directly affected by worm's burden, the lower percentage of eosinophils in our study might relate to lower intensity of infection, although the phase of disease may also contribute as an important factor in this regard.
About 100 million people in endemic areas of the world are infected by S. stercoralis, displaying different clinical symptoms such as eosinophilia. 15In this investigation, 7/11 (63.6%) of the patients infected with S. stercoralis had eosinophil count higher than normal range.In a study carried out by Ashrafi et al, 150 patients with an elevated level of eosinophils were evaluated.Their results showed that 63 (42%), 9 (6%) and 1 (0.7%) of them were infected by S. stercoralis, Fasciola spp.and Trichostrongylus spp. 14 another study in which 76 individuals with proven strongyloidiasis were evaluated, 82.6% had eosinophilia. 22ome researchers have demonstrated the main role of eosinophilia in the diagnosis of S. stercoralis and reported this parameter as a good indicator of infection with this worm among farm workers on the Mediterranean Coast of Spain; however, all these studies have simply kept the count of eosinophil which is not a sufficient determining factor in the diagnosis of S. stercoralis.
In our study, 3/10 (30%) of the patients with hymenolepiasis showed elevated percentage of eosinophil.Ajami and Rafiei also reported an increase in the percentage of eosinophils in the patients infected with H. nana in comparison with that in the control group; however, the difference was not significant. 25The results of a study demonstrated that H. nana oncosphere-derived molecules cause the intestinal eosinophilia in mice and can induce eosinophilia up to 15% in about 7% of the infected individuals. 26,27ccording to many researches, eosinophil counts were prominent in the patients infected with Hookworms. 28,29  the present study, 2 out of 3 (66.7%)patients infected with Hookworms had eosinophilia.
The percentage of eosinophil was only elevated in 1 out of 9 (11.11%)cases infected with E. vermicularis.Although it is claimed that E. vermicularis is an almost harmless intestinal helminth and could play a role in educating the immune system, it can sometimes cause eosinophilia. 30he relationship between trichostrongyliasis and different intensities of eosinophilia has been proven. 27,31 n the same vein, 3 out of 4 (75%) patients with trichostrongyliasis, in our study, had elevated eosinophilia.Elevation of eosinophil level to about 52% of leukocytes/mm 3 in blood was found in a patient with trichostrongyliasis in France. 32ystic echinococcosis (CE) is a frequent infectious disease among different animals as well as humans in Middle East as an endemic area 33 .Although it is believed that eosinophilia is seen in less than one quarter of the  cases of hydatid cyst, 27 38.5% (5/13) of our cases were identified with eosinophilia.Protozoan infections infrequently cause peripheral eosinophilia.The intestinal coccidian like Isospora belli and Sarcocystis hominis 16,17 can be related with eosinophilia.Furthermore, there are some reports about the relationship between malaria (Plasmodium falciparum) and eosinophilia. 34mong the patients infected with protozoa in our study, only few cases of giardiasis and blastocystosis showed an eosinophil count higher than normal range respectively.
Various studies on Blastocystis have recently been flourished. 35,36Our results showed that 2/20(10%) of the individuals infected with Blastocystis hominis had an increased percentage of eosinophils.
Some of the studies in the field of Giardia and eosinophilia are the case reports 37,38 and there are no considerable number of studies conducted on larger sample sizes in this regard.In a study carried out by Ashrafi et al, only 2.7% of the patients with high percentage of eosinophils had giardiasis. 14In our study, 3 out of 26 (11.5%) persons infected with G. lamblia showed higher percentage of eosinophils.
In this study, the percentage of eosinophils was compared between the individuals with parasitic infections.Generally, our findings are in line with a lot of available results on parasitic diseases and eosinophilia.The Fasciola spp.and S. stercoralis as the most important helminthic infections that cause tissue exposure showed higher levels of eosinophilia among helminthic infections.A few number of the patients infected with G. lamblia and B. hominis as protozoan diseases also showed high eosinophil counts.Eosinophilia could be a useful marker especially in the diagnosis of Fasciola spp.and S. stercoralis in helminthic infections, and in this particular context G. lamblia and B. hominis should be further noticed.

Table 1 .
The Prevalence of Eosinophilia in Individuals With Different Parasitic Infections

Name of Parasites No. of Patients (Male/Female) Range of Age No. Patients with Eosinophilia (Male/Female) Percentage of Patients with Eosinophilia (Male/Female)
In this study, the percentage of eosinophils was evaluated in the patients infected with different pathogenic/nonpathogenic parasites, and the worms examined were: Fasciola spp., Strongyloides stercoralis, Hymenolepis nana, Hookworms, E. vermicularis, Echinococcus granulosus, Trichostrongylus orientalis, Taenia saginata and Ascaris lumbricoides.