COMPARATIVE EFFICACIES OF DNA AND LIVE OOCYSTS VACCINES AGAINST EXPERIMENTAL INFECTION WITH LOCAL AND HOUGHTON STRAINS OF EIMERIA TENELLA IN BROILER CHICKENS

COMPARATIVE EFFICACIES OF DNA AND LIVE OOCYSTS VACCINES AGAINST EXPERIMENTAL INFECTION WITH LOCAL AND HOUGHTON STRAINS OF EIMERIA TENELLA IN BROILER CHICKENS

Abstract:

The search for a sustainable cost effective vaccine against coccidiosis that will be attractive to all poultry sectors has so far yielded the identification of novel recombinant DNA vaccine candidates such as Apical Membrane Antigen-1 (AMA-1). This study was aimed at evaluating the efficacy of vaccination of broiler chickens against coccidiosis using Eimeria tenella AMA-1(Et AMA-1) DNA vaccine in comparison to live vaccine based on body weight, gross caecal lesion score, oocyts production, histopathology, haematology and changes in serum enzyme levels of the immunized and challenged broiler chickens. A total of 80-day old broiler chickens were assigned to eight groups (1, 2, 3, 4, 5, 6, 7 and 8) of 10 each. At 14 days of age, the birds in groups 1(unchallenged unvaccinated control group), 2, 3 (challenged control groups for Local (L) and Houghton (H) E. tenella strains respectively) and group 4 (vector control group) were given 0.1 ml Phosphate Buffered Saline (PBS) on thigh muscle. Chickens in groups 5 and 6 (DNA vaccine group challenged with L and H strains respectively) were vaccinated with 0.1 ml of 100 μg of EtAMA-1 vaccine plasmid in PBS PH (7.6) by intramuscular injection on the thigh muscle and a repeat dose was given a week later (at day 21). Birds in groups 7 and 8 (Live oocysts vaccine group challenged with L and H strains respectively) were administered 0.2 ml Livacox® in 200 ml chlorine free clean water. At 28 days old, all chickens except group 1 were inoculated orally with 1 × 104 sporulated oocysts of the local and Houghton strains of E. tenella. A day prior to the experimental inoculation and seven days later, 2 ml of blood was collected from each bird by cardiac puncture for haematological and serum biochemical analyses. The birds were weighed aday prior to and reweighed 7 days after viii challenge to determine the weight gain after which they were sacrificed for postmortem examination, gross lesion scores, oocyst production and histopathology. There was a significant decrease (p < 0.05) in the mean body weight of infected unvaccinated birds (groups 2, 3 and 4) (15.4 %, 15.4 % and 19.2 %) respectively when compared with infected vaccinated groups (42.3 % and 50.0 %, for groups 5 and 6, 45.2 % and 46.2 % for groups 7 and 8 compared to the uninfected control group 1 (100%). Both vaccines were able to significantly (p <0.05) reduce the effects of E. tenella on gross lesion score (1.4 ± 0.86, 1.0 ± 0.92, 1.0 ± 0.92 and 1.0 ±0.62) for groups 5, 6, 7 and 8 compared to (4.0 and 3.4) of unvaccinated infected group 2 and 3 respectively. The relative oocyst production for the vaccinated groups 5, 6, 7 and 8 were 45 %, 44 %, 34 % and 29 % respectively compared to 100 % for unvaccinated groups 2 and 3 respectively. There was observable decrease in mean PCV values (24.6 % and 24.8 %) for unvaccinated groups 2 and 3 respectively compared to 27.4 %, 27.6 %, 27.2 % and 26.8 % for vaccinated groups 5, 6, 7 and 8 respectively. There was a significant decrease (p < 0.05) in mean total plasma protein and significant increase (p < 0.05) in AST and ALP values in unvaccinated groups compared to the vaccinated groups. There was an overall higher Anti Coccidial Index (ACI) of 177, 179, 180 and 179 for vaccinated groups 5, 6, 7 and 8 compared to 170 and170 of unvaccinated groups 2 and 3, respectively. In conclusion, EtAMA-1 DNA vaccination ameliorated the effects of E. tenella infection in broiler chicks comparable to live oocysts vaccination. Combinations of two or more antigens into a single DNA formulation is recommended with hope of achieving protection that is comparable to live oocyst vaccine.

COMPARATIVE EFFICACIES OF DNA AND LIVE OOCYSTS VACCINES AGAINST EXPERIMENTAL INFECTION WITH LOCAL AND HOUGHTON STRAINS OF EIMERIA TENELLA IN BROILER CHICKENS

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