Dr. Asghar Abbas1, Dr. Muhammad Asif Raza1, Dr. Muhammad Rizwan2 and Dr. Rao Zahid Abbas3
- Department of Veterinary and Animal Sciences, Muhammad Nawaz Shareef University of Agriculture, Multan, Pakistan
- College of veterinary Sciences, Bahauddin Zakruiya University Multan Layyah Campus
- Department of Parasitology, University of Agriculture, Faisalabad, Pakistan
Introduction
Poultry coccidiosis is most important parasitic disease of poultry, it is an infection of intestine which is caused by the protozoan which belongs to family Eimeriidae and genus Eimeria. The incidence rate of coccidiosis can range from 5 to 70% in commercial poultry. Clinical manifestations of disease include intestinal haemorrhage, malabsorption, diarrhoea, reduction of body weight gain due to inefficient feed utilization, impaired growth rate in broilers and reduction in egg production in layers. Coccidiosis is known as the parasitic disease which causes greatest economic loss on poultry industries throughout the world including Pakistan. Coccidiosis effects poultry industry because of production losses and costs for treatment or prevention. About 6–10% of all broiler mortalities occur due to coccidiosis. Coccidiosis cause heavy economic loss to poultry industry of world due to reduction in growth rate and poor feed conversion efficiency.
Immunological Control
Due to increase in problems in controlling coccidiosis such as resistance to anticoccidial drugs we need shift our strategy from chemotherapeutic control towards vaccination to control poultry coccidiosis in Pakistan. Vaccines can serve as excellent alternatives to anticoccideal drugs for effective control of coccidiosis. During the past several decades scientists have done a lot of work to develop different types of vaccines in Pakistan and other countries for controlling coccidiosis but the problem is the delay in progress to develop various types of vaccines. The progress in research on vaccine development of different types of vaccines are given below.
First live Anticoccidial vaccine named as Coccivac came into market in 1952 and after some years years a second live vaccine, Immunocox, came into the marketplace. Until now, five more live vaccines have been developed and are commercially available in different parts of the world. Out of newly developed five vaccines Paracox and Livacox, are composed of attenuated strains of Eimeria spp and third vaccine which is named as Nobilis COX ATM, is a nonattenuated mixture of Eimeria spp (Vermeulen et al., 2001). The fourth and fifth vaccines which are named as Advent and Inovocox, are nonattenuated mixtures of E. acervulina, E. maxima and E. tenella. Many other live vaccines are under devolopment and some of them are introduced in some countries. Initially, live vaccines were administered in layer and broiler breeder birds at time of placement as chicks. But, from the last ten years its use has also increased in broiler birds as well. Vaccination is an effective and best alternative method to use of anticoccidial drugs for mainly two reasons. First, research have proved that vaccines give a comparable level of protection to growing broiler chicken against coccidiosis. Moreover, it has also been demonstrated that use of live vaccines replaces the indigenous populations of coccidia with susceptible coccidial populations especially in broilers.
In Pakistan mostly imported live vaccines are used for control of coccidiosis. Among these, two imported vaccines which are named as Immucox and Coccivac are commercially available in Pakistan. There has been different trials conducted for evaluation of locally prepared Eimeria vaccine to control poultry coccidiosis. But, use of live vaccines for control of coccidiosis have limited benefits because It only works for a short period and have no advantage in continuous control of sporulation of oocyst due to which there is continuous chance of reemergence of coccidiosis.
Previously, it has been proved that due to adaptation of Eimeria tenella isolates (egg adopted vaccine) on chicken embroyos, it can be used to obtain antigenic material at large scale in Pakistan and other countries of world. Furthermore, several reports have demonstrated that sporulated oocysts of Eimeria speciese also provide the protection against challenging coccidian infections and induce the immunological response against coccidian infections.
Recent research in Pakistan has shown the immunological effects of gametocyte vaccine from the local isolates of Eimeria tenella on birds infected with coccidiosis. Gametocyte vaccine show remarkable immunological effects and protection against mixed species coccidian infections in birds. Results shown that gametocyte vaccine containing additional gametocyte protein of 49.23 kDia provide maximum protection against mixed coccidial infections. The protection aginst mixed Eimeria infections is due to high molecular weight of gametocyte protein as similar effects were also observed in another study by using the gametocyte vaccine prepared from isolates of Eimeria maxima. Different studies in Pakistan have confirmed that gametocyte vaccine is more effective as compared to livacox vaccines. Local gametocyte vaccine increased weight in broiler chickens infected with coccidiosis as compared to livacox vaccine.
Latest research on induction of immunity against avian coccidiosis have proved that immunity can be induced through the use of antigen loaded exosomes isolated from Eimeria dendritic cells( DCs). The birds immunized with Ag loaded exosomes and infected in vivo with eimeria oocysts have shown to improve the weight gain, FCR, reduced oocyst shedding, overcomed intestinal lesions and reduced mortality as compaered to those which were unimmunized. These results suggest that these antigen loaded exosomes can be successfully used as fied vaccination against Avian coccidiosis.
Devolpment in DNA Vaccine
There has been no work done on DNA vaccine on avian coccidiosis in Pakistan. So, there is need to work on DNA vaccine in Pakistan. Recently, it is reported that Immune responses induced by DNA vaccination can be further increased by co-injection with recombinant cytokines or plasmids or through the co-expression of antigens with cytokines.
