Sheep are considered one of the most important small ruminant livestock globally (1). They represent a major source of wool, meat, milk, and skins, which together form a vital component of the rural economy, mainly in arid and semi-arid areas (2). In Egypt, sheep and goats are among the most important animals for meeting the requirements for meat for human consumption (3). However, this industry is subjected to a wide variety of parasitic infections that affect the health status of animals, causing great losses in the livestock industry (4). Among others, infection of sheep by gastrointestinal parasites (GIP) is one of the major health problems in the sheep industry, leading to a loss of plasma protein, alterations in protein metabolism, diarrhea, and a loss of body weight. Additionally, the infection by these parasites suppresses the immune system of the infected animals, which in turn makes them more susceptible to other pathogenic agents (5).

Haemonchosis is regarded as a highly destructive disease that significantly reduces the productivity of infected sheep and has substantial economic consequences. This includes elevated levels of morbidity and mortality and increased management costs associated with implementing control measures (6, 7). The disease is caused by Haemonchus spp. or barber’s pole worm, which is considered a principal abomasal worm of ruminants with a worldwide distribution. Nearly 12 species have been recognized in domestic ruminants (8). Among others, Haemonchus contortus is considered the nematode of greatest economic importance in small ruminants (9) and extremely pathogenic in sheep (10). Subclinical infection with H. contortus can lead to reduced weight gain and appetite. Moreover, heavy infection by these worms might result in the progression of various clinical signs that involve weight loss, submandibular edema, and diarrhea (11). Additionally, these parasites are voracious blood suckers, and therefore, heavy infection by the parasite can cause lethal anemia and might lead to death in heavily infected animals (12). Given its veterinary importance with regard to the health and productivity of sheep, periodical updates about the disease at a national level is very important for providing effective control measures for the disease.

Taken into account, Haemonchus spp. has a direct life cycle. The adult female inhabits the abomasum or intestine and then immature eggs pass in the stool. Later, immature eggs develop in the external environment and hatch to give first-stage larva (L1). Larvae nourishment is mainly based on bacteria, and then they molt to the second larval stage (L2) and undergo another molt to reach the infective third larval stage (L3). Sheep contract the infection through third-stage larvae (infective stage) during grazing, which then reach the final predilection site and develop to L5 (13). Environmental conditions, mainly temperature and humidity, influence the survival of the larvae of Haemonchus (14, 15). In this regard, cool and humid climatic conditions favor the survival of L3 for several months. By contrast, L3 might survive for a shorter time in warm weather due to the higher metabolic rate that speedily reduces energy reserves (16, 17). The identification of Haemonchus spp. could be achieved by several approaches, including direct fecal smears, fecal flotation for detecting parasitic eggs, the rearing of eggs in culture to obtain L3, and postmortem examination to determine immature and adult worms (18). However, these methods have low sensitivity and lack the ability to distinguish the circulating species/genotypes. On the other hand, fecal culture methods for the identification of nematode larvae followed by the screening of positive samples using PCR-based techniques possess many advantages and might help confirm the infection (19). As shown in Table 1, few epidemiological and molecular studies have explored the occurrence of Haemonchus spp. circulating in Sheep in Egypt, particularly in the upper part of the country (19–36). Based on information provided by previous studies, this study was undertaken to morphologically and molecularly identify Haemonchus in sheep. Additionally, the research included a comprehensive review of previous studies on the various Haemonchus species circulating among sheep in Egypt.

The current study has unveiled intriguing parasitological and molecular insights into Haemonchus infection among sheep in Upper Egypt, along with an exploration of the primary risk factors linked to this infection. Furthermore, the study conducted a national-level review of haemonchosis prevalence, with detection rates ranging from 7.00 to 49.00% (Table 1). In the present study, the overall prevalence of Haemonchus infection was 33.00% (132 of 400), which was one of the highest values for Upper Egypt and, clinically, the positive animals displayed symptoms such as emaciation, anemia, reduced appetite, and diarrhea. Taken into account, very few molecular studies have been conducted at a national level and the majority of the previous studies were based on macroscopical methods for the identification of the parasite. At a national level, Haemonchus spp. were microscopically identified among 30.00% of the examined animals in a previous study in Egypt (24), which is slightly lower than our present results. In other nearby countries, a previous study (52) in Tunisia obtained a lower prevalence rate of 17.00%. Similar results (34.51%) were reported in a previous study in Iraq (53). By contrast, a study in Sweden (54) found a higher prevalence rate of 56.00% using microscopy and 72.00% through ddPCR. Another Swedish study (55) identified H. contortus in 37.00% of the examined sheep. Furthermore (56), a study in Rwanda recorded a prevalence rate of 83.40% for Haemonchus spp. These variations might be attributed to differences in climatic conditions, geographical locations, management practices, and the methodologies employed for pathogen detection (14, 15).

In this study, age was recorded as a significant factor affecting Haemonchus infection in sheep. In this respect, animals less than 2 years of age had a higher infection rate than that of older animals (p < 0.05). These findings agree with previous studies (53, 56, 57) in which the young animals were more vulnerable to infection than adults. The higher infection in young animals may be related to undeveloped active immunity at a younger age (58). In relation to the sex of the inspected sheep, the study exhibited no significant deviation (p > 0.05) between the sex of the infected animals, with prevalence rates of 36.70 and 31.40% in male and female sheep, respectively. This slight percentage difference may be attributed to the fact that most females are kept indoors for breeding under careful and clean management, while most males are allowed to graze outdoors, potentially exposing them to a higher risk of infection. Similar findings were reported by Aga et al. (57) in a previous study in Western Oromiya, Ethiopia. On the other hand, our results are not consistent with other previous studies (24, 53) that found that females were more susceptible than males. Another previous study (56) found a similar infection rate in male and female sheep. The seasonal variation was reported as another significant risk factor associated with Haemonchus infection in the examined sheep, with a rate of 58.90% (132 of 224) in cold or winter; no infections were identified in summer (p < 0.05). The obtained results agree with a previous study (55) that mentioned that the fecal egg counts of ewes decreases to insignificant levels in summer, and the infections tended to rise through autumn and were highest in lambs that persisted on the farms at the end of winter. Moreover, a previous study (59) concluded that Haemonchus spp. have a distinctive feature, which refers to inhibited development (hypobiosis). Seasonal changes have been planned to be the main factor of hypobiosis. The feature is initiated when occasions for the spreading of the larvae are limited, which is a parasitic variation in cold weather. Additionally, hypobiosis can occur in high temperature conditions during the dry season (i.e., low humidity conditions). Furthermore, it was mentioned that, in Mediterranean climate regions, including Egypt, the outlines of Haemonchus spp. infection in small ruminants is frequently biphasic, with the highest rates occurring from early autumn to early winter and also from late spring to early summer (59).

The diagnosis of gastrointestinal nematodes in sheep is commonly accomplished through stool analysis, with the identification of nematode species primarily relying on the morphology of eggs and larval stages found in feces. Importantly, many species of strongyle egg, such as Haemonchus, Trichostrongylus, Teladorsagia, Cooperia, and Bunostomum, are similar in size and shape (60). Consequently, they cannot be easily distinguished at the genus level. Therefore, it is clear that combining fecal culture and the molecular investigation of the third-stage larva (L3) is essential for the specific identification of gastrointestinal nematodes in livestock (61–63). The molecular detection of circulating species of parasites in a specific area is invaluable for understanding the disease’s epidemiology and implementing effective control measures to combat the infection. It is worth noting that the most prevalent molecular markers include cytochrome c oxidase subunit I (cox1) of mitochondria, NADH dehydrogenase subunit, and the internal transcribed spacers (ITS1 and ITS2) of ribosomal DNA, which have consistently served as genetic markers for identifying the strongyle species in domestic animals (62–66). In the present study, the phylogenetic analysis of PCR products from larval DNA revealed that the most prevalent nematode causing GIP problems in sheep flocks in Assiut was H. contortus (61, 67, 68).

This study addressed the prevalence of haemonchosis in sheep from Upper Egypt, identifying one of the highest levels recorded in the region. It was observed that some individual variable factors, such as age and the time of the year, appear to influence the risk of H. contortus infestation. Updated knowledge of these aspects can increase the efficiency of diagnostic and control methods, thereby reducing the associated risks of this disease. Our current study highlights the substantial advantages of combining morphological and molecular techniques for haemonchosis detection in sheep. This approach has facilitated the identification of the H. contortus species in the studied samples. This species demonstrates a high biotic potential, leading to rapidly increasing parasitic loads that impact health and limit productivity. In terms of the costs associated with control through chemical treatments, significant direct and indirect losses occur, contributing to a decline in sheep productivity, profitability, and sustainability. Considering these findings, we recommend that future studies delve into the extensive prevalence of nematode species on a broader scale in Egypt. This approach is crucial for the epidemiological study and management of Haemonchus spp.

The original contributions presented in the study are publicly available. This data can be found at: https://www.ncbi.nlm.nih.gov/nuccore/; OP984151.

The animal studies were approved by research ethical committee of the Faculty of Veterinary Medicine, Assiut University (Approval number 06/2023/0096). The studies were conducted in accordance with the local legislation and institutional requirements. Written informed consent was obtained from the owners for the participation of their animals in this study.

SM: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Resources, Supervision, Validation, Writing – original draft, Writing – review & editing. AD: Conceptualization, Formal analysis, Investigation, Project administration, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. ER-Á: Data curation, Formal analysis, Funding acquisition, Methodology, Validation, Visualization, Writing – review & editing. FA-A: Conceptualization, Formal analysis, Funding acquisition, Investigation, Methodology, Software, Validation, Visualization, Writing – original draft, Writing – review & editing. FO: Conceptualization, Methodology, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. AG: Data curation, Formal analysis, Investigation, Resources, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing. AF: Data curation, Funding acquisition, Validation, Writing – original draft. DS: Data curation, Software, Validation, Writing – original draft. ME-K: Funding acquisition, Resources, Software, Validation, Writing – original draft. DB-B: Software, Validation, Writing – original draft. AA: Investigation, Writing – original draft. EE: Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Resources, Software, Validation, Visualization, Writing – original draft, Writing – review & editing.