How field trials prove to determine efficacy

26Aug 2016
The Guardian Reporter
The Guardian
How field trials prove to determine efficacy

Veterinary vaccines have had, and continue to have, a major role in protecting animal and birds’ health and public health, reducing animal and chicken suffering,

enabling efficient production of food animals to feed the burgeoning human population, and greatly reducing the need for antibiotics to treat food and companion animals and birds in general.

In Tanzania field trials to determine efficacy and safety of a new village chickens vaccine has proved successful by more than 95 percent.

Speaking at the just ended 5th Annual National Science, Technology and Innovation (STI) conference and exhibitions being held in Dar es Salaam, the lead scientist in this first of its own kind discovery, Sokoine University of Agriculture (SUA) Prof Philemon Wambura named the vaccine as Tatu Moja Thermostable.

The Tatu Moja Thermostable, a novel thermostabilised trivalent vaccine effectively works against the Newcastle disease, Fowlpox and Infectious coryza in multi-age free ranging village chickens.

The vaccine can be used for simultaneous control of the three diseases in village chickens. It enhances vaccination coverage especially in rural areas with limited or no cold chain facilities.

This could significantly reduce high morbidity and mortalities caused by these diseases thus enhance poultry productivity which in turn will lead into increased poultry contribution to household income, nutrition and poverty alleviation.

According to Prof Wambura, the vaccine which is currently awaiting different companies to commercialise, it was discovered at a tune of USD6 million, part of it is from the Tanzania Commission for Science and Technology (COSTECH).
How the field trials were conducted

Explaining how it was conducted, Prof Wambura said that the trials were conducted in Singida, Bahi and Mvomero Districts where a total of 1,495, 129 and 74 chickens were vaccinated with trivalent vaccine (ND+FP+IC), through eye drop, respectively making a total of 1,698 chickens.

Then blood samples were collected aseptically from brachial vein of each chicken on days 0, 30, 60 and 120 after vaccination. Thereafter extracted sera were tested by haemagglutination-inhibition (HI) assay and the results were recorded.

Thirty days after vaccination of chickens with the trivalent vaccine, it was observed that no adverse reactions were reported from all vaccinated chickens. Moreover, the trivalent vaccine against ND, FP and IC recorded safe, efficacious and protective in chickens vaccinated under the field conditions.

Why the scientists developed interest in discovering the vaccine?

According to Prof Wambura, among the livestock species, poultry especially village or local chickens form a common resource to which the disadvantaged social groups and those who do not possess cattle, sheep or goats attach high socio-economic value.

They provide the vital protein in terms of eggs and meat and when eggs and live chickens are sold they generate household incomes. Besides the supply of food, the chickens fulfil a range of other functions for which it is difficult to assign a monetary value.

Citing an example, he said that they are active in pest control, provision of manure, used in special festivals and traditional ceremonies and meeting social obligations.

Therefore, increasing poultry productivity would result into positive impacts on household food security and poverty alleviation both in terms of increased dietary intake and income generation, respectively.

Nevertheless, village chicken farming is characterised by high morbidities and mortalities that limits its growth. High mortalities in village chickens are believed to be caused by a number of factors that include mismanagement, lack of supplementary feeding, predators and diseases.

But, diseases are believed to be the main limiting factor to the production of village chickens. Among the diseases, respiratory poultry diseases remain to be the most important as they are the major killers of multi-age village chickens in many parts of the country.

The respiratory diseases cause high mortality rates (up to 90 percent) and sometimes devastate whole flocks during outbreaks. Many of these diseases or infections once re-emerged or introduced into a geographic area can explode into an epidemic and may have a significant negative effect on flock numbers.

Respiratory diseases are continuing to cause high economic losses in village chickens due to increased mortality rates, decreased weight gain and increased feed conversion rates.

Although vaccination is recommended as the most appropriate way of protecting chickens against these diseases, conventional vaccines used in commercial chickens, have little success in village chickens.

The village chickens, being in multi - age flocks, scattered in small numbers over villages, are difficult to catch for formal vaccination as adopted in commercial chicken enterprises.

More importantly, these conventional vaccines are heat labile and therefore require complex cold-chains to link the vaccine producers and users. Furthermore, these vaccines are relatively expensive and produced in large-dose units suitable for large commercial flocks.

Therefore, innovative techniques to produce vaccines suitable for rural condition with no cold facilities and with small-multi-age flocks are required.

While, currently there are vaccines for control of ND, there are no suitable commercially available vaccines for control of FP and AP in village chickens.

The new discovered Fowlpox, a different and effective vaccine
The Fowlpox vaccines are available worldwide but there are reports that these vaccines are contaminated with Reticuloendotheliosis virus (REV) which is immunosuppressive.

The previously developed autogenous vaccine seed for FP vaccine is not REV contaminated, thus could overcome contamination problem if optimised and field tested.

Circulating strains of ND virus are capable of causing 100 percent mortality in unprotected flocks. Outbreaks of ND are unpredictable and discourage villagers from paying proper attention to the husbandry and welfare of their chickens.

Furthermore, it has been observed that there is re-emergence of Fowl pox and IC in areas where ND has been controlled. Poultry respiratory diseases, due to mixed infections by different organisms are very common, hence using bivalent, trivalent or polyvalent vaccines is preferable than that of monovalent vaccines for prevention of the common respiratory diseases.

In addition, bi-, tri- or polyvalent vaccines have the advantages of reducing vaccination expenses and saving time and labour costs.
Until recently there has been no provision of vaccines for ND, FP and IC in remote areas due to lack of cold chain facilities and simple delivery methods that can be applied by farmers. However, under this study, these obstacles were overcome through the development of easy to administer thermostable vaccines.

The eye drop and oral routes of administration of the developed vaccines can be applied by community vaccinators or farmers with minimal training.

The recently developed vaccines which can be stored up to 4 weeks under room temperature and are in small vials so that large losses ascribed to higher volume of vaccine formulation are eliminated compared to alternative commercial vaccines.
The results from laboratory trials

The results from laboratory trials have shown that the trivalent vaccine against ND, FP and IC is safe, efficacious and therefore may be used in controlling these diseases. This study therefore aims at determining the field efficacy of the combined vaccines against the respiratory diseases of poultry namely ND, FP and IC.

Earlier, the Director General for the Tanzania Commission for Science and Technology (COSTECH), Dr Hassan Mshinda commended the discovery saying the commission will continue supporting such discoveries which aimed at generating income and also improving people’s lives.

He said that the discovery has come at a right time because Tanzania is having huge population of local chickens in rural areas where electricity is not well distributed to support cold chain system for vaccine storage. These Thermal stable vaccines are ideal for rural environment where electricity is an issue.

He said that the Commission has supported other discoveries and innovations in the field of agriculture, energy, water, health, information and communication technology and technology transfer among many others.

“We are also supporting innovative, business cluster, and incubation, value addition of local produce and natural resources and environmental management for sustainable industrialisation,” he said.

“COSTECH deals with the coordination and promotion of technology development and scientific research. Therefore, we feel encouraged by these good results, some which have already reached the end users,” he said.

The conventional vaccines against various chicken diseases have not been successful due to their heat liability. In addition, the nature of village chickens in multi-folk-multi-age and difficulty of catching individual chickens for vaccination had made it difficult to use the conventional vaccines.

The thought solution for these shortcomings was to develop thermostable vaccines which can be administered without necessarily catching individual birds.

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