SEROPREVALENCE OF MALIGNANT CATARRHAL FEVER-RELATED OVINE GAMMAHERPES VIRUS IN CATTLE

Malignant catarrhal fever (MCF) is a worldwide viral, non-contagious disease that is transmitted to cattle. It is determined to be a significant source of economic loss for several ruminant species. It is mainly caused by ovine herpesvirus-2 (OvHV-2), which affects the epithelial and lymphoid tissues of the respiratory and digestive tracts. There are limited data on MCF in Egypt, and there is no epidemiological investigation of the clinical prevalence of MCF in Assiut governorate. So the aim of this work is to study the clinical occurrence of MCF at Manfalut center in Assiut governorate, and serological detection of MCF infection in cattle. A total of 30 cows suspected infected with MCF were screened using enzyme-linked immunosorbent assay (ELISA) test. Each investigated cow's age, sex, breed, admission time, and contact with sheep were recorded in order to determine the prevalence of MCF. Records included fever, lymphadenitis, corneal opacity, erosions in the buccal cavity, abnormal breathing, purulent nasal discharge with the nasal ulcer, and diarrhea. Overall, 10% of the examined cows were affected. The seroprevalence of MCF infection was higher in native female cows aged 1-3 years, which had previously interacted with sheep, particularly in April and May, although statistical analysis did not reveal a significant difference. Cattle are more likely to get infected if raised in the same grazing area as sheep and goats. As a result, we advise keeping cattle grazing areas distinct from those used for sheep and goats


INTRODUCTION
Malignant catarrhal fever (MCF) is a globally distributed viral disease (Plowright, 1986).currently emerging as a significant source of economic loss for several ruminant species.The disease was initially discovered species, including domestic cattle, buffalo, pigs, horses, and several species of deer, have been shown to experience intermittent, lymphoproliferative, and multisystemic effects from MCF (Metzler, 1991).High fever, frequent nasal discharge, ocular opacity, widespread lymphadenopathy, leukopenia, severe inflammation of the nasal, oral, and conjunctival mucosa, and necrosis extending to the trachea and esophagus are among the clinical signs.There may occasionally be skin rashes, diarrhea, non-suppurative arthritis, and CNS symptoms (Schock and Reid, 1996;Pardon et al., 2009;O'Toole andLi, 2014 andÇitil, M. andUzlu, E., 2017).The term MCF refers to a couple of diseases that are not distinguishable clinically or pathologically, but are associated with two different pathogens.Neither of these viruses affects the primary hosts (wildebeests and sheep) or spreads from one animal to another.The first disease is called wildebeest-associated MCF virus (WD-MCF), also referred to as Alcelaphine herpesvirus-1 (AlHV1), and it is a new genus of Macavirus (previously known as Rhadinovirus) of the subfamily Gamma herpesvirinae in the family Herpesviridae.The second disease is called sheep-associated MCF virus (SA-MCF), and it is also a Macavirus of the subfamily Gamma herpesvirinae known as Ovine herpesvirus-2 (OvHV2), which is transmitted to cattle from sheep.(Nelson et al., 2013 andLi et al., 2014).Although MCF-like signs have long been observed in Egypt, the disease has never been officially confirmed, and the causative agent wasn't identified until Bastawecy and Abd El-Samee (2012) isolated it from water buffaloes and calves.The geographical distribution of SA-MCF animal cases is approximately equal in Upper and Lower Egypt.This can be explained by the fact that sheep in Damietta, El-Gharbia, El-Sharkia, Dakahlia, Kafr El-Shiekh, Giza, Fayoum, and El-Menia had the virus in 2013-2014 and that infected animals (cattle and buffaloes) had MCF clinical signs (Zaki et al., 2016).Currently, few data on MCF are available in Egypt, and there is no epidemiological investigation of the clinical prevalence of MCF in the Assiut governorate.The goal of the work is the serological detection of MCF in cattle and the epidemiological study of the clinical occurrence of MCF in Manfalut Center at Assiut Governorate.

Ethical approval
All procedures were carried out following the ethical regulations established by Assiut University's institutional ethics committee.Thirty cattle of different breeds, ages, and sexes belonging to Manfalut Center in Assiut Governorate were admitted to the Veterinary Teaching Hospital of the Faculty of Veterinary Medicine at Assiut University between April and October 2023.The cattle under examination had corneal opacity, purulent nasal discharge, bloody diarrhea, enlarged superficial lymph nodes, fever, and mouth lesions (erosions and ulcers).All cows were treated in accordance with the guidelines established by Assiut University on animal research, and samples were taken only with the owners' permission.

Study area
The current study was carried out in Assiut Governorate between April 2023 and October 2023.The animals under investigation came from Manfalut Center in Assiut Governorate and were admitted to the Veterinary Teaching Hospital at Assiut University Faculty of Veterinary Medicine.

Animals and samples.
This study included a total of 30 cows of different ages, sexes, and breeds.Only cows exhibiting one or more clinical signs of malignant catarrhal fever infection (high fever, corneal opacity, lymphadenitis, erosions of the oral and nasal mucosa, abnormal respiration, nasal discharge, and bloody diarrhea) were included.Serum samples were drawn directly from the jugular vein of diseased cattle by using clean, dry, sterile syringes, put in vacutainer tubes without anticoagulant, and then used for ELISA test.

Data collection and clinical examination
Data obtained from each cow included the age (less than one year, <1-3years, and <3-5years), sex (male or female), breed (native, Friesian), time of admission (April-May, June-July, and August-September), and contact with sheep.Physical examination included body temperature measurement, visual examination of mucous membranes, and checking for signs of respiratory illness and digestive disturbances.Cattle with high fever, profuse nasal discharge, ocular opacity, lymphadenitis, erosions of the oral and nasal mucosa, which may spread to the esophagus and trachea, central nervous system symptoms, and blood-stained feces will be included in the study.

ELISA test
The ELISA test kit (Chongqing Biospes Co., Ltd., BZEK 1949) was used to detect OvHV-2 antibodies in the serum of suspected cows according to the manufacturer`s manual.

Statistical analysis
To measure the impact of each factor individually on the prevalence of the disease in cattle (i.e., age, sex, breed, admission time, and contact with sheep) and the association of clinical signs with the occurrence of the disease (i.e., temperature, corneal opacity, lymphadenitis, erosions of the oral and nasal mucosa, abnormal respiration, nasal discharge, and diarrhea), relative risk was calculated and chi-square tests were performed using SPSS statistics software (IBM Corp, USA, Version 29).A probability value (P-value) less than 0.05 was considered statistically significant.

Clinical findings.
The thirty cows in this investigation displayed one or more of the usual clinical symptoms of MCF disease.A wide variety of clinical symptoms were recorded, which may vary from case to case.26 cows were suffering from high fever, 24 of them with enlargement of superficial lymph nodes (Figure 1).20 cows showed erosions and ulcers in the oral mucosa (Figure 3).Respiratory distress was seen in 8 cases, and 10 cases showed mucoid to mucopurulent nasal discharge, and only one case showed an ulcer in the nasal mucosa (Figure 4).There were 13 cases of diarrhea, 7 of which had bloody diarrhea.Four cases had corneal opacity (Figure 2), and it was discovered that 17 of the cases had previously come into contact with sheep.The clinical signs seen in cows of different breeds, ages, and sexes are shown in Table 1.

Results of ELISA test.
The overall seroprevalence of MCF infection in examined cows was 10% (3/30) using the ELISA test.12.5% of 24 cases showed enlarged lymph nodes, especially the prescapular and prefemoral lymph nodes, and 11.3% of 26 cases had a persistent high fever.10 % of the 20 cases had oral lesions, including ulcers and erosions.10 % out of the 10 cases exhibited purulent nasal discharge.Only one case with a nasal ulcer had a positive result, and none of the patients with irregular breathing did.10% out of 20 cases with oral lesions, such as erosions and ulcers.Of the six cases of diarrhea, 33.3% had positive results.However, none of the cases involving bloody diarrhea had positive results.In all cases with bilateral corneal opacity, the result was negative (Table 2).

Risk factors associated with MCF prevalence.
Compared to other age groups, cows between the ages of one and three years had a higher infection rate (13.3%).Our results also showed that the infection rate in females (12.5 %) was higher than in male cows (9.1%).Two of the three positive cases (14.3%) were admitted to the clinic in April and May, and we discovered that all three instances (15%) were of the native breed.It 266 was reported that two cases of the positive cases (11.8%) had previously come into contact with sheep.According to Table 3, there was no significant variance found in the statistical analysis of these risk factors.Furthermore, Murray and Blood (1961) reported that no disease other than MCF frequently exhibits the combination of mucosal lesions, corneal opacity, and persistent fever.
The severity of the disease varies according to immunological status, age, and coinfections in cattle, and not all affected animals show clinical symptoms.Clinical findings associated with MCF infection can be explained by lymphoid proliferation and infiltration, widespread vascular epithelial lesions, and involvement of the vascular adventitia.These factors also explain the development of gross lesions, such as epithelial erosions, that are linked to lymphoid cells like CD8+ T lymphocytes, which are the predominant cells linked to the vascular lesions, and OvHV-2 replication in lung tissue.Because sinusoidal cells are the preferred sites for gamma herpesvirus replication in lymphoid tissue, such as OvHV-2, the enlargement of the lymph nodes is caused by the abnormal proliferation of these cells (Zaki et al., 2016, andConstable et al., 2017).
The seroprevalence of MCF infection and disease symptoms did not differ statistically, except for one case with a nasal ulcer that had very high statistical significance (Table 2).The severity of the clinical manifestations and the stage of the disease may help to explain this, as nasal ulcers usually occur in the later stages of the disease.This case was in the last stage of the disease, showing all its other severe signs, and died shortly after the collection of the sample.et al. (2003), this could be explained by 1-to 2-year-old cows contracting the virus and losing their maternal immunity.Additionally, we found that April and May had the highest infection rates of the year.This is consistent with the findings of Blood et al. (1983), who discovered that the late winter and early spring months have the highest disease incidence.Since the owners of Manfalut Center typically keep native breeds indoors and in contact with sheep, higher MCF seroprevalence was observed in native cows.On the other hand, Friesian cows are typically kept on farms apart from small ruminants.It is also possible that the higher seroprevalence of the disease in females than in males is due to the fact that local owners usually keep female cows for milk production and reproduction.
The majority of positive cases in our study had previously been raised with lambing ewes and recently weaned lambs, and these findings are consistent with those of Li et al. (2004).Most cases of SA-MCF are caused by cattle coming into contact with lambing ewes and freshly weaned lamb.Cattle can contract MCF from sheep infected with OvHV-2, and the incidence of infection rises when sheep and cattle are housed together (Plowright, 1990 andFenner et al., 1993).

CONCLUSIONS
In conclusion, raising goats and sheep in the same grazing area as the susceptible species can increase the risk of infection.Thus, we suggest separating grazing areas for sheep and goats from those used for cattle and buffalo.Additionally, extensive research on the ages of sheep and goats is necessary to determine the suitable age at which to infect susceptible species with MCF.

Figure
Figure 2: 3-years native cow with corneal opacity

Table 1 :
The reported clinical signs in examined cattle in each age, sex, and breed.

Table 2 :
Association of clinical signs of MCF infection with the results of ELISA test in examined cattle.

Table 3 :
Factors associated with MCF seroprevalence among the examined cases.