The seroepidemiological condition of malaria in three main districts of Hormozgan Province, a low transmission area in southeast of Iran, was investigated.
Malaria is an infectious disease transmitted by the
Malaria has been considered as a threat in Iran with a high morbidity rate in the last decades [
The predominant species of parasite in southern part of Iran is
The use of thin and thick smears for the diagnosis of malaria was conducted in 1900 and even nowadays it is considered as the gold standard in the diagnosis of malaria. Studies have shown that serological methods, for the diagnosis of malaria, can be considered as an effective tool in epidemiological studies and prevention programs of malaria, since these methods are able to detect previous exposure or contact with the disease.
Measuring the prevalence of anti-malaria antibodies (seroprevalence) is a valuable approach for defining the status of malaria transmission in a given area and also a useful method for malaria surveillance [
As ELISA method consists of simplicity and low cost, compared with other serological methods, and is able to evaluate multiple samples simultaneously; therefore, in this study, ELISA method was used for the seroprevalence evaluation of malaria in a low transmission area of malaria in Iran.
The current study was conducted in three main districts (Bandar Lengeh in the west, Bandar Abbas in the center, and Bandar Jask in the east) of Hormozgan Province, located in the southeast of Iran. Hormozgan is one of the 31 provinces in Iran and its provincial capital is Bandar Abbas. In 2011, Hormozgan Province had a population of 1,500,000 people. Hormozgan Province maintains a long warm (9 months) season and a short (three months) cool season. The province is one of the warm and dry regions of Iran, with warm and humid coastlines in summer, where the temperature climbs up to 52°C. The average annual temperature of the region is about 27°C. The province is considered as a malarious province in Iran.
After getting approval from the Ethics Committee of Shiraz University of Medical Sciences, blood samples were taken from 803 healthy volunteers from three main districts of Hormozgan Province including Bandar Lengeh (171 samples), Bandar Abbas (457 samples), and Bandar Jask (153 samples). The samples were taken from the tip of the left second finger of each subject with the help of a disposable lancet. Three drops of blood were collected from each participant onto a filter paper (Whatman 3 MM), dried at room temperature, sealed in a plastic bag, and stored at −20°C until use. Cluster sampling, based on the population of each district, was used for sample collecting. These three districts are in National Malaria Control Program areas in Iran and names of the head of households were available in local health centers. Cases were randomly selected from these files and reached either in their house or in the health centers. Informed consent was obtained from the subjects before sampling.
Trager and Jensen (1976) method was used for continuous culturing of
The blood spot on filter was punched with a paper punch and each punch was placed in a well of a U shaped ELISA microplate. Extraction of sera from filter papers was performed as previously described with some modification [
ELISA microplate was sensitized with 5
Standard
The mean age of participant was 27.4 years (range 1–74). Males constituted 58.3% of the subjects and 41.6 of them were females. The overall seroprevalence of malaria was 8.7% (70 out of 803 samples). The number of positive cases in Bandar Abbas was 15, in Bandar Lengeh it was 51 samples, and in Bandar Jask it was 2 cases. A significant correlation was found between seropositivity and place of residence. The highest seroprevalence of malaria (13.2%) was seen in the age group of 11–20 years. Seropositivity was higher in low educated individuals. Correlation between seropositivity and gender, age, and educational levels of the participants was significant. Table
Demographic characteristics of participant and relative seropositivity to malaria in Hormozgan Province, southern Iran.
Characteristics | Frequency (number) | Percent (%) | Positive for anti-malaria Ab. |
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Number | % | ||||
|
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Male | 469 | 58.3 | 15 | 3.2 | <0.05 |
Female | 334 | 41.6 | 55 | 16.47 | |
|
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1–10 | 54 | 6.75 | 1 | 1.43 | <0.05 |
11–20 | 106 | 13.26 | 14 | 13.2 | |
21–30 | 369 | 46.18 | 37 | 9.75 | |
31–40 | 161 | 20.15 | 10 | 6.21 | |
41–50 | 70 | 8.76 | 2 | 2.86 | |
51 and higher | 39 | 4.9 | 1 | 1.43 | |
|
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Bandar Abbas | 457 | 58.51 | 15 | 3.28 | <0.05 |
Bandar Lengeh | 171 | 21.89 | 51 | 29.82 | |
Bandar Jask | 153 | 19.59 | 2 | 1.31 | |
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Uneducated | 82 | 10.28 | 1 | 1.2 | <0.05 |
Primary and secondary level | 281 | 32.25 | 31 | 11.1 | |
Postsecondary level | 253 | 31.74 | 32 | 12.64 | |
University level | 123 | 15.4 | 6 | 4.87 |
Despite the significant advances that have been made over the years to control malaria, the disease is still a major health problem in the world and about one hundred of the countries or regions of the world are among the malaria-endemic areas [
Several studies pointed out that serological markers are valuable tools for evaluating and monitoring of malaria transmission [
Moreover, in this study filter paper has been used for sample collecting which has several advantages. Perhaps the most important advantage is the elimination of blood sampling from the vessels, which often in infants and children have been the subject of debate. In epidemiological studies, obtaining blood samples from the vessels due to the required equipment is more expensive than obtaining blood samples from the capillaries. Another important advantage of this method is the ease of transfer and storage of samples before experiment. The method is less invasive and also reduces the risk of disease transmission.
In the present study, 8.7% of the participants had anti-
The seroprevalence of malaria in this study is lower compared with those studies conducted in other regions of the world. This might be related to the success of malaria control programs in the region and implies that eradication of the disease in the province in the coming years is feasible [
A very low level of seropositivity to malaria (about 1%) was reported in a previous study in another district (Bashagard) of the province. The main explanation of this low seropositivity is that the study has measured anti-malaria antibodies (IgG, IgG1, and IgG3) by ELISA, using either PvMSP-119 or PfMSP-119 antigens, instead of using a pan-malaria antigens [
In this study, seropositivity and gender were significantly associated. In total, women had more antibodies compared to men. The reason for that is not clear since both males and females are equally exposed to
In the current study, the highest seropositive cases were from the age group of 11–20 years and the lowest in the age group of 1–10. The lower seroprevalence in children below ten years indicates less exposure of individuals and probably lack of local transmission of malaria. Higher rate of seropositivity in postsecondary educational level, in comparison with primary and secondary levels, may also be related to the age of the subjects rather than educational level.
Some of the seropositive cases in this study may have parasite, though at very low level, and may act as malaria reservoir, contributing to the persistence of malaria transmission. These seropositive asymptomatic cases may be a big challenge for malaria elimination program in any endemic area.
The study of Nateghpour et al. on 408 patients with suspected malaria symptoms microscopically detected
Taken together, the findings of this study demonstrated a relatively low rate of seropositivity of malaria in Hormozgan Province, southeastern Iran.
The results described in this paper were part of M.S. thesis of Fatemeh Nejati.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The study was financially supported by the Office of Vice-chancellor for Research of Shiraz University of Medical Sciences.