Prevalence with risk factors associated with Theileria annulata in cattle of Babylon province, Iraq

Introduction

Theileriosis is a haemoprotozoan disease transmitted via biting of ticks and this disease leads to major economic losses in livestock including cattle (Kundave et al., 2015) [9] . Ticks (ixodid ticks) act as vectors in spreading of the disease in hot or moderate climates that inject Theileria spp. into the bovine blood. Eight different Theileria species cause bovine theileriosis including Theileria annulata, Theileria parva, Theileria orientalis, Theileria velifera, Theileria lowrenci, Theileria tarigtrgi, and Theileria sergenli that produce moderate or asymptomatic sickness in cattle (Khudor et al., 2022) [8] . The most typical clinical signs initially are anorexia, elevated body temperature, enlargement of the superficial lymph nodes, pale mucous membranes, then iteration dehydration, saliva in the mouth, lacrimation, nose discharge, nervous signs, and breathing problems at the later stages (Faraj and Assi, 2022) [5] . The prevalence and active regions of vector ticks are critical components of bovine Theileria species epidemiology. The disease, which is difficult to completely eliminate, is associated with obvious regional and seasonal epidemics. Severe infections of cattle result in death, which causes considerable economic losses and potential threats to the cattle industry.

Materials and Methods

Sample Collection

120 Blood samples of cattle (43 male and 77 female) were collected during the period from (September 2025 to January 2026) randomly from the south of Babylon (Al-Qassim, Alhamaza al-gharbi, AL-Talia and Al-shomali). Blood is usually collected from jugular vein of each cattle using vacuum tube then, 5 ml of blood was drawn by a sterile needle with a vacutainer EDTA-sterile tubes and immediately transported in the ice box for laboratory diagnosis (microscopic examination).

Microscopic Examination Blood Smear

Blood samples were used to make thin and thick films, which were then allowed to air dry, fixed with 100% methyl alcohol for 15 minutes, and stained with 10% Giemsa stain for 30 minutes before being examined under an x40 light microscope, according to Rashmi (2013) [13] .

Staining with Giemsa stain

Giemsa stain is one of the synthetic dyes used to differentiate parasites. Prepare blood film, air dry and place in a staining rack (put drop from blood and make Thin blood smear) the blood smear is fixed in absolute methanol for 3-5 minutes. -Staining is performed at room temperature for 15-30 -Wash thoroughly with running water. The smear surface is washed directly.

Statistical analysis

Statistical analysis was performed using Microsoft Excel 2010 and SPSS for Windows version 27. Using the chisquared test, differences between groups were examined. Zhao et al. (2022) [17] used P-values less than 0.05 as the significance criterion for all statistical studies.

Results

The results of microscopic examination in the present study found that the total infection rate of Theileria annulata in cattle was 27.5% (33/120), as shown in Table (1).

Table 1: Total rate of Theileria annulata infection in cattle by microscopic examination in Babylon province

Number of examined animals

Number of infected animals

% of infected 120 33 27.5%

According to sex, the females had a greater overall infection rate (37.6%) with Theileria annulata than males (9.3%) (Table 2). These findings suggest that geographical factors play an important role in the distribution of Theileria annulata infection. The higher prevalence observed in certain regions may be related to differences in tick density, environmental and climatic conditions, animal management practices, and the effectiveness of control measure Chi-square analysis revealed a statistically significant difference in Theileria annulata infection among the examined regions (p < 0.05).

Discussion

The present study revealed a relatively high prevalence of Theileria annulata infection among cattle in southern Babylon province, with an overall infection rate of 27.5%. This finding indicates that tropical theileriosis continues to represent a major parasitic challenge for cattle production systems in endemic regions. Similar prevalence levels have been reported in areas characterized by favorable environmental conditions for tick survival and transmission (Uilenberg, 1995; Jongejan and Uilenberg, 2004) [15,7] . The higher infection rate observed in female cattle compared to males may be attributed to prolonged exposure to tick infestation due to longer retention of females within herds for breeding and milk production purposes. In addition, physiological stress associated with pregnancy and lactation has been shown to reduce immune competence, increasing susceptibility to tick-borne infections (Radostits et al., 2007). Comparable trends were reported by Brown (1997) [3] , who indicated that management-related stressors significantly influence the epidemiology of tick-borne diseases in cattle. Age-related analysis demonstrated that calves less than one year old exhibited the highest prevalence of T. annulata infection. This increased susceptibility in young animals can be explained by the immaturity of their immune system and the absence of acquired immunity against the parasite. Norval et al. (1992) [12] reported that repeated exposure to Theileria spp. leads to partial immunity in older cattle, resulting in reduced clinical disease and lower detectable parasitemia. Similarly, Dolan (1989) [4] highlighted that infections in adult cattle are often subclinical due to the development of immune tolerance. Marked regional variation in infection rates was observed in the current study, with Al-Shomali region showing the highest prevalence. This variation strongly suggests the influence of environmental and ecological factors such as humidity, vegetation density, tick abundance, and grazing systems. Bishop et al. (2004) [2] emphasized that ixodid tick distribution is closely linked to climatic conditions, which directly affects the transmission dynamics of Theileria annulata. Furthermore, inadequate implementation of tick control measures may contribute to the persistence of infection in highly affected areas (Gharbi et al., 2011) [6] . The significant association between infection prevalence and geographical location highlights the importance of targeted control strategies based on regional risk assessment. Integrated tick control programs, improved herd management, and early diagnosis are essential to reduce the economic impact of tropical theileriosis (OIE, 2018). Overall, the findings of this study confirm that Theileria annulata infection in cattle is multifactorial, influenced by host-related and environmental factors, and remains a major constraint to cattle productivity in endemic areas. The microscopic study by analysis of Giemsa-stained for blood samples, the confirms that Theileria annulata infection rate in cattle is widespread in Babylon province, recorded overall prevalence was 27. 5%. And the data, rate of infection were significantly with the factors such as age, gender, and geographic. The Female showed a higher prevalence rate while the males were lowest. The young cattle in age groups one year old were the most affected highest prevalence rate in Al-Shomali, recorded the higher infection rate the role of environmental conditions and tick density in disease transmission. Further research the molecular diagnostic approaches are advised to improve detection accuracy and to better understand the epidemiology of Theileria annulata in Iraq.

Conclusion

The present study concluded that Theileria annulata infection is prevalent among cattle in Babylon province, with an overall infection rate of 27.5%, as confirmed by microscopic examination of blood smears. This finding indicates that bovine theileriosis remains an important parasitic disease affecting cattle health and productivity in the study area. The results demonstrated a significant effect of sex on infection rate, where females showed a markedly higher prevalence (37.6%) compared to males (9.3%) (p < 0.05). This difference may be attributed to physiological stress, pregnancy, lactation, and management practices that increase females' susceptibility to tick infestation and infection. Age was also identified as a significant risk factor for T. annulata infection (p < 0.05). Cattle less than one year old exhibited the highest infection rate (53.1%), suggesting that younger animals are more vulnerable due to their immature immune systems and limited prior exposure to the parasite. Furthermore, a statistically significant variation in infection rates was observed among different regions of Babylon province (p < 0.01). The highest prevalence was recorded in Al-Shomali, indicating that geographical location, tick density, climatic conditions, and animal husbandry practices play crucial roles in the epidemiology of bovine theileriosis.

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