The current findings indicated that the prevalence of intestinal protozoan infections was 30.9% based on a single stool sampling. This infection rate was low compared to a previous study carried out on 37,000 outpatients in which the prevalence of intestinal protozoa was 53%
[5]. In comparison to other Mediterranean countries, the infection rate with intestinal protozoa in this study is higher than previous reports from Saudi Arabia among patients seeking health care (27.8%–32.2%)
[15],
[16], Iran (19.9%)
[17],
[18] and Oman (18%)
[19], however lower compared to the prevalence in Pakistan (52%)
[20]. The most dominant protozoa in this study were
G. duodenalis and
E. histolytica/dispar, which were rated at 17.7% and 17.1%, respectively. This finding was comparable to the previous studies carried out in Yemen
[6],
[10], except studies among restaurant workers
[7],
[8]. These differences could be attributed to the differences in the study subjects and study areas. Besides that, different diagnostic methods used from one study to another should also be considered as a possible reason behind the disparity in the infection rates
[21],
[22]. This study showed a significant association between low personal hygiene practices and behavior with intestinal protozoan infections. Logistic regression analysis indicated that people who did not take their bath at least twice a week were at 2-fold higher risk of getting infection with intestinal protozoa. Undoubtedly, the current water crisis contributed in some ways to the low hygienic practices in Yemen, leading to the increase of intestinal parasitic diseases.
Yemen depends totally on ground water, which is dropping by 20–65 feet a year as reported by the World Bank
[23]. Furthermore, the Carnegie Endowment for International Peace noted that 19 of Yemen's 21 main aquifers were not being replenished because of lower rainfall
[24]. The impact of water quantity on the health status has been well documented since plentiful and accessible supplies of water do encourage better hygiene. Two review studies which covered 84 studies in 28 countries have concluded that quantity of water available has more impact on endemic diarrhea cases in developing countries than water purity
[25],
[26]. Another study carried out in Nicaragua found that children from homes with insufficient water supply had 34% higher infection rate of diarrhea
[27]. Water availability may also affect the frequency of hand washing as it has been stated that a mother needs 20 liters of water to wash her hands after using the latrine, changing a nappy, before preparing food, eating, giving food to the infant and handling of cooking or drinking utensils
[28].
In the present study, logistic regression analysis also showed that those people who came in contact with animals were at significant risk in acquiring protozoan infections. This association implicated animals as a significant source of protozoan infection in Yemen. However, this postulation should be confirmed by further studies which incorporate molecular tools. It is common for the rural communities in Yemen to keep animals such as cattle, goats and donkeys in the ground floor of the same house. Evidence of zoonotic transmission of some intestinal protozoa, especially
Giardia and
Cryptosporidium have been provided by several studies via molecular data analysis
[29],
[30].
With regards to
Giardia infection, it has been shown to be significantly associated with drinking untreated water. In Yemen, ground water is the main source of drinking water. Given that most of the homes are without a proper sanitary system, the possibility of faecal contamination is high via ground seepage
[31]. Furthermore, it was noted that people in rural areas are dependent on dams besides wells as drinking water resources. Dam water is a collection of rainwater, which is exposed to high pollution, especially during the rainy season due to soil runoff contaminated with parasite (oo)cysts and ova from animal and human faeces. Previously, the using of well water has been identified as significant predictors of
E. histolytica and
Giardia infections in Saudi Arabia. Comparatively, those who use desalinated water have the lowest degree of exposure to the risk of infection
[32]. Contamination of drinking water with
Giardia cyst during transporting and storing of drinking water are highly possible as rural people in Yemen use containers to transfer water from the dams or wells to the houses where water is stored to be used for drinking and cooking. Faecal contamination of drinking water between the source and the point of use is well known
[33] and improving household water management has been promoted as low cost health intervention to combat waterborne infections
[34].
As for
E. histolytica/dispar infection, the present findings showed that those who do not practice proper hand washing before eating was at two fold higher risk of acquiring
E. histolytica/dispar infection. The major role of contaminated hands in the faecal-oral transmission of diseases has been well documented in developing countries and washing hands before eating or after defecation has been considered as a secondary barrier. In Indonesia, it has been reported that people who never or sometimes wash hands had a four times higher risk of getting severe diarrhea
[35]. In Nepal, the practice of hand washing had a strong correlation with the prevalence of parasitic infection
[36]. Another case-control study in the same country indicated that people who never used soap for washing hands were at 30 times higher risk of typhoid
[37]. In addition, not washing hands has been reported to be significantly associated with diarrhea in Malaysia
[38] and Myanmar
[39]. Intervention trials and case-control studies, conducted in Bangladesh, have also indicated that not washing hands was a significant risk for diarrhea
[40],
[41],
[42].
In addition, animal contact was also identified as a significant factor associated with
Entamoeba infection. Although it is still unclear whether
Entamoeba infection is zoonotic or not, this parasite has been isolated from animals. In Ethiopia, a study on baboon and Cercopithecus (old world monkey) found that the prevalence of
E. histolytica was 24.4%
[43]. Another study carried out in Ethiopia found that cockroaches serve as carriers of human intestinal parasites
[44]. In Uganda,
E. histolytica and
Giardia have been detected in monkeys
[45]. Similarly, in the Philippines,
E. histolytica and
E. dispar were detected among captive macaques in a primate facility. In the same study, using PCR, they found that 23
E. histolytica isolates were identical to human
E. histolytica [46] highlighting a possibility of zoonotic transmission.
In conclusion, the present study showed high prevalence of intestinal protozoan infections with E. histolytica/dispar and G. duodenalis being the most predominant protozoa among patients seeking health care in Yemen. Low personal hygiene practices such as not washing hands before eating and the frequency of bathing, besides water contamination seemed to play major roles in the high transmission of intestinal protozoa. Therefore, these factors should be given due consideration when implementing any interventions to combat these intestinal protozoan diseases. Although animals are still a possible source of human infection with protozoa as shown in this study, this postulation warrant further studies especially those that utilize advanced molecular techniques. Genotyping E. histolytica/dispar and G. duodenalis from human, animals and water resources are highly recommended to understand the actual dynamics of transmission of these protozoa in Yemen. Likewise, the authority must take into consideration the development of health awareness among the community through active encouragement of individuals in adopting hygienic behaviors via audio, visual and curriculum programs. Radical solution to water scarcity is also an important requirement to combat the proliferation of these infections in Yemen.
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