In present study, the overall prevalence of contagious ecthyma in goats was recorded in and around Parbhani district during the period from July, 2023 to January, 2024. Out of total 103 cases had typical clinical manifestation, 40 goats were found positive for contagious ecthyma virus on the basis of PCR indicating 38.83% disease prevalence. Different researcher has found higher and prevalence than current research results which might be due to collection of random sampling irrespective of sex, age, breed and health status of goats (Tandale et al., 2023). Maximum affected goats were in 0–4 month of age group (53.44%), more prevalence may be due to incomplete development of immunity compared to adult age group goats. Statistically highly significant difference (P < 0.01) in prevalence might be due to their fragile epithelium of skin, which makes the virus entry more easily in body in young age group of goats.
The severity of infection was higher in young age group (< 1 year) due to exposure to primary infections and poor immunity against infections. Nursing animals showed higher prevalence than non-nursing animals due to the difference in the chance of contact with the infected neonates during suckling period. In addition, nursing animals had more likely to develop stress and compromised immunity due to suckling which makes them more vulnerable for infection stated by Tedla et al., (2018). However, due to immature immune systems, young animals were more susceptible to infection and had more serious scabby lesions, which sometimes lead to in death (Spyrou and Valiakos, 2015). Whereas, Esmaeili et al., (2021) reported that goats with older age develop immunity against the virus and therefore, disease was less common in older animals. They observed that, prevalence and severity of infection was higher in the young age group of goats.
The male goats were slightly more predisposed to CE but statistically non – significant difference recorded. It might be due to unequal sample size with respect to gender, rearing of more number of male goats over female for meat purpose and more aggressive behaviour of male goats (Tandale et al., 2023). The higher prevalence rate of contagious ecthyma was recorded in non-descript goat which could be due to rearing of more non-descript breed in and around Parbhani city. Whereas, in order to get a clearer picture, sampling from a larger population of different breeds will provide more information on the breed predisposition to infection Jesse et al., (2018). Also, higher prevalence was recorded in poor than medium and good health condition of goat. The body condition of goats was strongly correlated with prevalence of the virus in which poor body conditioned goats showed a higher prevalence compared to good and medium body conditioned goats. This was associated with the development of strong immunity in well-nourished animals compared to less nourished goat (Tedla et al., 2018).
The distribution of lesions in affected goats were more obviously observed on nostrils followed by oral commissures, muzzle, lips followed by ear, gums, coronary band, tongue, udder and teat. The lesions were recorded commonly on the nostrils, oral commissures, muzzle and lips might be due to more readily exposure of these body part while feeding on dry hay or hard fodder, spiky weeds and prickly plants and might have chances to enter and initiate infection of orf virus when comes in contact with infected animals. Orf virus is epitheliotropic and causes vacuolization and hypertrophy in keratinocytes from the external spinous layer of the epidermis resulted in reticular degeneration with marked epidermal proliferation with intra-epidermal and intra-dermal micro-abscesses and crust formation on the surface (Fleming et al., 2015).
The decreased haemoglobin levels might be due to many factors, including the direct effect of virus on the erythrocytes, which can cause their destruction, as well as the development of anaemia occurs due to decreased food and water intake by the goats. In addition, the virus may also cause damage to the bone marrow, resulted in a decreased production of new red blood cells, leading to decreased haemoglobin levels. The reduced level of TEC might be due to bone marrow destruction and also by injury to the scab lesions during grazing or feeding which cause blood loss. The increased TLC level in contagious ecthyma goats might be due to body immune system responds releasing signaling molecules called cytokines and due to secondary bacterial infection. The immune response can stimulate the bone marrow to produce more leukocytes, leading to an increased in overall TLC count. The elevated TLC count is a part of defense mechanism against the viral invader as WBC plays a crucial role in fighting infection.
The neutrophilia might be attributed to neutrophils are the first line of defense against a viral invasion and due to secondary bacterial infection. Neutrophils migrate immediately to the site of infection to fight against the pathogens that infect the damaged. The lymphocytopenia was recorded which might be due to virus can directly affects the lymphocytes or trigger responses that lead to their depletion. A virus directly target and infects lymphocytes leading to their destruction, causes bone marrow depression where lymphocytes are produced, virus replicates in cell causing death and exaggerated immune response cause damage to lymphocytes leading to lymphocytopenia.
PCR assay showed to be very rapid, accurate and cost effective for diagnosis of contagious ecthyma without using cell culture system or electron microscopy during field outbreak and quick confirmatory test for orf virus detection by Sowmiya et al., (2018). Molecular diagnosis of orf viral antigen in scab samples could be competently done by semi-nested PCR as it detects low copy number of viral DNA and found more efficient diagnostic method for orf virus in goats (Sunder et al., 2020).
For molecular confirmation of orf virus, 103 scab samples were collected from contagious ecthyma suspected goats. For extraction of DNA from scab samples, Phenol:Chloroform: Isoamyl alcohol (25:24:1) technique was used. For amplification of PCR, B2L gene (592 bp) of CEV can be used and it could amplify the desired gene product as low as 160 ng/µl for CEV detection (Sowmiya et al., 2018). The B2L gene encodes for a extremely immunogenic major envelope protein and able to induce both antibody and cell mediated immune responses. Therefore, B2L gene used for confirmation of contagious ecthyma virus by PCR (Inoshima et al., 2000).
Nucleotide sequences are essential for precisely determining the specific CEV variant for the field sample. In addition, use of phylogenetic analysis, the nucleotide sequence data can also be employed to determine the percentage homology and/or divergence of the obtained sequences to that of the sequences of various geographical areas in the database.
The complete nucleotide sequences of B2L encoding gene of three goat orf virus from Parbhani district, Maharashtra, India were compared with each other as well as with related virus B2L gene sequences available in the GenBank using ClustalW alignment implemented in software MEGA 11. The Sandlapur_PBN_orf, Purna_PBN_ORFV_orf and Parbhani_orf having accession numbers PP235095, PP235096 and PP235097, respectively and showed 99.47% identity with MH790950 (Meghalaya) and 99.30% identity with MF567363, MF567362 (Parbhani), MG334559 (Goa), MG365666, MG365656 (India) and JN846834 (Assam). All three strains from study displayed, 99.12% identity with MH756172 (Banglore) and MF567361 (Parbhani). While, 98.63% identity with DQ263305 (India), MT875449 (Mukteshwar), OQ971953 (Pondicherry) and MT350784 (MP) whereas 97.44% identity with MH998254 (JK) at nucleotide level.
Based on a partial sequence of the B2L gene, evolutionary analysis and multiple sequence alignment revealed that all strains under investigation belonged to the same clade. Analysis of the phylogenetic tree formed using nucleotide sequence of the B2L encoding gene revealed that, the three orf virus isolates from goat inhabiting Parbhani area clustered with the other ORFV isolates from different geographical areas of the India. Also, the three obtained sequences were closely related with each other and with other strains obtained from GenBank for the Parbhani district, Maharashtra. The similarity was based on nucleotide homology and phylogenetic analysis.
The sequence information acquired in the present study would be useful for the development of a suitable vaccine against ORFV strains in India. In addition, for the development of ultimate therapeutic and proper control measures for its eradication. In spite of the fact, the virus phylogenetic analysis suggests a hypothetical origin. The present research suggested that, the disease might have come about by the importation of animals for meat or as a result of better cross-breeding practices intended to increase goat productivity.
Goats in all treatment groups showed significant improvement in clinical and haematological parameters after treatment with 0% mortality and 100% recovery rates. Full recovery time required in group I, II & III was recorded in around 11, 9 and 16 days. During recovery the major portion of scabs were fell off and lesions were completely healed uneventfully along with no new scab formation on the body parts. There was statistically significant difference noted between recovery periods for three group treatment protocol (Table 6).
Table 6
Average recovery period for three different treatment groups
Treatment No. | Group III | Group I | Group II | C.D. value (0.01) | C.D. value (0.05) | Significance |
Treatment Average | 16 | 11.9 | 9.4 | 2.795 | 2.069 | S |
Critical Difference (CD) Compared | a | b | c |