PREVALENCE OF LUMPY SKIN DISEASE IN CATTLE, IN RED SEA STATE, SUDAN

Abstract

Lumpy skin disease is an economically important disease which produces debility in infected cattle. The morbidity rate is about 2% to 98% while the mortality rate is estimated to be 3% or more. The purpose of this research was to study the prevalence of lumpy skin disease (LSD) in Red Sea State, Eastern Sudan. Two outbreaks of LSD that occurred in Red Sea State in March 2003 to August 2005 were investigated. The clinical diagnosis was confirmed in the laboratory by virus isolation and identification. Clinically, the disease was characterized by fever, nasal discharge and salivation for about 3 days. The skinraches soon developed into nodules, 0.5 to 5 cm in diameter, which appeared on the neck, brisket, back and thighs. Occasionally nodules were seen on the udder, vulva, scrotum and around the eyes and lips, odema of legs and brisket and enlargement of lymph nodes, depression, emaciation and loss of appetite were frequently observed. A variation in the severityof the lesion was noticed and that had been severe in crossbred animals in comparison to local ones. In the investigated outbreaks, all age, sex and breed groups were affected. However, more than 50% of the deaths were reported in young animals in comparison with adult cattle. To determine the sero-epidemiology of LSD in Red Sea State, the agar gel immunodiffussion test was used to detect antibodies in serum samples collected from cattle of two different breeds, sex and age distributed in different areas. Out of500 test serum samples, 341 samples gave positive result (68% seropositive). On the other hand, 285 serum samples out of 500 were positive when tested by serum neutralization test (57% seropositive). Seropositivity is higher when AGID test was used in comparison to serum neutralization test. IX Serological testing using AGID and neutralization tests applied on sera collected from local and crossbred cattle resulted in higher seropositive in crossbred cattle (90% for the AGID and 63% for SN test) than in local breed (76.4% for the AGID and 43.0% for SN test). It is obvious that the crossbred animals are more susceptible to this disease. With regard to sex, seropositivityin females was higher (73.6 for AGID, 54.6% for SN test) than in males (58.6 for AGID, 44.7% for SN test). Concerning the age, seropositive was higher in the age 0 – 1 year (100% for the AGID, 70.4% for SN test) followed by the age 1 – 3 years (97.7 for the AGID, 68.3% for SNtest) and lower in age above 3 years (59.8% for the AGID, 46.8% for SN test). This result indicates that this disease is prevailing mostly in young animals at the age of 0 – 3 years. With regard to area, seropositivitywas higher in Tokar (88 for the AGID, 75% for SN test) and Port Sudan (64 for the AGID, 59.5% for SN test) and lower in Sinkat (57% for the AGID, 18% for SN test) and Haya (42 for the AGID, 12% for SN test). The LSD is found to be more spreading between animals reared in Tokar area followed by Port Sudan and then Sinkat. Haya area showed a very limited prevalence of LSD disease among the animals. In the present study, the skin scabs and nodules were collected from sick animals, homogenized and inoculated in LT cell culture. Four virus isolates were obtained when 5 skin samples were inoculated in lamb tests (LT) cell culture (Port Sudan 1,Port Sudan 2, Tokar and Sinkat). These isolates produced characteristicCPE of LSDV, such as rounding of cells and cell clumping or shrinking and plaque formation when inoculated in LT cell culture. The CPE progressed slowly with cell X detachment leaving irregular holes. Spindle-shaped cells with long extremities at the margin of the holes were also seen. The affected cells exhibited a conspicuous granular appearance and irregular hole and rounding up of some cells were also observed. Titration of isolates of lumpy skin virus (Port Sudan 1, Port Sudan 2, Tokar and Sinkat) was performed inLT cells and resulted in a titer of 10 5.2 /ml, 10 4.2 /ml, 10 4.3 /ml and 10 3.6 /ml, respectively. The virus neutralization test was used as confirmatory test for diagnosis of lumpy skin disease and for comparing it with polymerase chain reaction (PCR). LT cells infected with Tokar isolate were used and the results were taken after 9 days. The results confirmed the identity of lumpy skin virus isolates used in the present study since the test gave a neutralization index of 1.4. Polymerase chain reaction (PCR) was used in this study to determine the feasibility of improving diagnosis of lumpy skin disease virus in scabs collected from the field, as well as in supernatant of infected cell culture. Two methods of DNA extraction were tried. The first method (PCR1) employed on DNA extraction step with scabs homogenate or cell culture supernatant added directly toPCR mixture at 99°C for 15 min to release the DNA and then followed by ordinary PCR. By this method, 1 out of 5 samples gave positive result. In the second method (PCR2), viral DNA was extracted by phenolchloroform specimens, four samples out of 5 gave positive results. The DNA band sizes corresponded to the expected size of 192 bp. PCR2seemed to be more sensitive than (PCR1) method. Finally certain recommendations are given in this aspect.