Serologic and cross-immunity studies with contagious ecthyma and goat pox virus isolates from the western United States

Development of a contagious ecthyma vaccine for goats

OBJECTIVE

To identify a strain of contagious ecthyma virus from goats that possesses the appropriate characteristics for an effective vaccine for goats.

ANIMALS

25 goat kids used for vaccine development and 100 goat kids used for evaluation of vaccine efficacy.

PROCEDURES

5 strains of contagious ecthyma virus were tested in a vaccination-challenge study to identify the best strain to be the seed strain for a contagious ecthyma vaccine. The vaccine derived from the chosen viral stain was tested at 2 concentrations for efficacy in a vaccination-challenge study.

RESULTS

2 of 5 viral strains induced moderate to severe scabs following infection, and 3 viral strains protected the goats from wild-type virus challenge following vaccination. Viral strain 47CE was selected as the seed source for the production of a contagious ecthyma vaccine because of the larger vaccine-to-challenge scab formation ratio. Vaccine 47CE protected all goat kids (48/48) following challenge with the wild-type contagious ecthyma virus; all goat kids (32/32) in the control group had scab formation following challenge with the wild-type contagious ecthyma virus, which indicated no protection following administration of vaccine diluent.

CONCLUSIONS AND CLINICAL RELEVANCE

A vaccine containing a caprine strain of contagious ecthyma virus used in goats appeared to provide the characteristics needed for an effective vaccine, including good scab production and protection from wild-type infection. This vaccine may potentially provide better protection for goats from contagious ecthyma than currently available vaccines labeled for sheep.

A comprehensive review of goat pox and sheep pox and their diagnosis

Sheep and goats occupy a premier place in the livestock industry and contribute significantly to the world economy. Their populations are threatened by a number of health hazards, among the most notable of which are goat pox and sheep pox. These diseases inflict substantial losses in terms of reduced productivity and lower quality of wool and leather. They pose a major obstacle to the intensive rearing of sheep and goats and considerably hamper international trade. A comprehensive knowledge of goat pox and sheep pox would help in the diagnosis, prevention and control as well as the management of these diseases in a proper and effective manner. Although the two diseases are easily identified from the clinical signs and host species affected, laboratory tests are needed for confirmation. A battery of simple but highly efficient diagnostic methods and reagents is available for goat pox and sheep pox. However, the best way to control these diseases is the prophylactic immunization of all susceptible animals with a potent and efficacious vaccine, especially in areas where these diseases are endemic.

Lack of cross-protection between vaccinia virus and orf virus in hysterectomy-procured, barrier-maintained lambs

Hysterectomy-procured, barrier maintained lambs were immunised with either of virus or vaccinia virus and subsequently challenged with both viruses. Under these conditions lambs were protected from challenge with the homologous virus but no cross-protection was observed. The feeding of colostrum that contained antibodies to orf virus had no effect on the duration of viral lesions. Immunoblotting analysis and ELISA of serum samples taken during the course of the experiment indicated that the animals mounted antibody responses to both viruses. The cross recognition of 3 vaccinia virus antigens by the hyperimmune anti-orf virus serum was revealed by immunoblotting.

Orf virus and vaccinia virus do not cross-protect sheep

Inoculation of lambs with a New Zealand strain of orf virus (NZ 2) failed to protect them against subsequent infection with the Lister strain of vaccinia virus. Similarly, in the reciprocal test, vaccinia virus failed to protect against subsequent orf virus infection. Inoculation with either orf virus or vaccinia virus alone afforded protection against reinfection with the same virus. These results have relevance to the use of vaccinia virus gene vectors in sheep.