Assessment of Newcastle Disease Virus Antibodies Among Birds Reared
CHAPTER ONE
Objectives of the Study
Broad objective
To determine the degree of improvement of ND immune response and productivity, in birds reared, through effective parasite control
Specific objectives
- To collect baseline data on poultry production systems, farmer demography and quality of eggs produced in Aba LGA.
- To establish the existing antibody titers to ND in chicken and recover ND virus in dry and wet seasons.
- To determine the effect of endo- and ecto-parasite control on the chickens response to ND vaccination and productivity (weight changes).
CHAPTER TWO
LITERATURE REVIEW
Poultry in Nigeria
There are 31.8 million domestic poultry in Nigeria, of these 25.7million (about 83.4%) are of indigenous type, while the rest are semi-commercial and commercial chicken (NBS, 2010). These chicken are a source of protein in form of meat and eggs. Local birds reared produce 54% and 75% of the total meat and egg, respectively, and their products fetch relatively higher prices compared to the commercial ones (Njue et al., 2002).
Chicken are reared under different production systems. In intensive production system, farmers keep exotic commercial broilers and layers, while in semi-intensive production system, genetically improved strains and crosses of local breeds with Rhode Island Red and Light Sussex are kept. Traditional, least-capital-intensive system, where birds are left free- ranging in the daytime and confined during the night, is normally used for indigenous village chicken (Njue, 1997). These village chicken are normally more resistant to local diseases than the exotic breeds and scavenge for their own feed with little or no supplementation (Bebora et al., 2005).
Benefits of poultry
Free range indigenous village chicken serves an important multipurpose function in the village economy. Poultry farming is practiced by 80% of the small scale and subsistence farmers, mainly women. Chicken and eggs have two major uses, namely: sell to generate income and home consumption, while manure is used in farms and gardens as fertilizer (Mwakapuja, 2009). Chicken also are used for cultural functions and ritual and in poor households, they are kept as convertible and accumulative assets that are available and easily traded for payments and other income requirements (Anderson, 2001). The sector provides employment to a number of groups in the communities such as farmers, traders, transporters; and restaurant, hotel and eateries‟ workers in villages and towns (Mwakapuja, 2009).
Constraints to poultry production
Diseases are a major hindrance to village chicken productivity. Apart from Newcastle disease (ND), other causes of mortalities and low productivity in village chicken include coccidiosis, fowl pox, fowl typhoid, fowl cholera, infectious coryza, chronic respiratory disease and endo- and ecto-parasites (Cumming, 1992; Maina, 2005; Sabuni, 2009). Mortalities due to diseases in birds kept under free-range system, where the only disease control measure exercised is vaccination against ND, is about 11% (Stotz, 1993). This is because ND is the major constraint causing huge losses. Other constraints include poor management practices, in particular poor nutrition and housing; predation; lack of formalized market; theft, low genetic potential; and poor husbandry. These result in high mortalities and reduced production. However Bebora et al. (2005) reported that some indigenous village chicken have a laying capacity comparable to that of the exotic breeds; a potential that can be nurtured to develop good lines of birds reared, without necessarily cross-breeding them with exotic breeds.
Newcastle disease
Newcastle disease (ND) is a viral disease of many kinds of poultry and wild birds characterized by marked variation in morbidity, mortality, signs and lesions. The virus is in the order Mononegavirales, family Paramyxoviridae and genus Avulavirus (Alexander, 1997).
Pathotypes of Newcastle disease virus
Newcastle diseasevirus (NDV) is classified into five pathotypes based on the predominant signs in affected chicken, which in turn are affected by the strain (Beard and Hanson, 1984). These are viscerotrophic velogenic (Doyle) form that causes an acute lethal infection characterized by hemorrhagic lesions in the digestive tract (Doyle, 1927), neurotrophic velogenic (Beach) form that causes, acute lethal infection characterized by respiratory and neurological signs (Beach, 1942), mesogenic (Beaudette) form that causes a less pathogenic form with mortalities in young birds, lentogenic (Hitchner) form that causes a mild or inapparent respiratory infection (Hitchner and Johnson, 1948); and the asymptomatic (enteric) form that mainly involves infection with lentogenic virus strain which causes no overt disease (Mcferran and Mc Craken, 1988).
Maintenance of the virus in village situation
The viral host range is wide and has been reported to affect 250 avian species with domestic chicken and turkey being severely affected (Alexander, 1998). Nyaga et al. (1985) indicated that ND outbreaks are reported during the cold and dry periods of the year with peaks in April, JuneJuly and September-November periods affecting all ages of chicken. Another study by Kasiiti
(2000) indicated that ND is widespread in village chicken and ducks in Nigeria. The study by Njagi et al. (2010b) showed that the virus is present in healthy hens and that those surviving outbreaks or have antibodies from previous exposure to ND may maintain the virus endemicity in the village chicken. Thus, carrier chicken, village poultry population dynamics, other poultry species, wild birds and heterogeneity of the virus are some of the risk factors that have been associated with the maintenance of NDV (Awan et al., 1994; Njagi et al., 2010b).
CHAPTER THREE
MATERIALS AND METHODS
Study chicken
Chicken of various age groups: chicks (under 2 months of age), growers (2-8 months of age) and adults (over 8 months of age) were used for the checking of levels of antibody titers during the wet and dry seasons while only growers were used for the checking of effect of parasite control on immune response following ND; the age groupings were done following the criteria given by Sabuni (2009). Determinations of respective ages were done subjectively, guided by farmers‟ information. The identified birds were bought and transported alive in cages to the Department of Veterinary Pathology, Microbiology and Parasitology, Faculty of Veterinary Medicine, College of Agriculture and Veterinary Sciences, Kabete Campus, for respective experiments. .
The minimal sample size was calculated using the method described by Martin et al (1987), as follows:
N = 4pq/L2
Where; N= sample size, p= prevalence (50%), q= 1-p and L= Limit of error on prevalence taken at 10%
= 4 *0.5*0.5 = 100
0.12
For statistical, animal welfare and financial reasons, 8 birds were used for each group for the seasonality and experiment to demonstrate effect of parasite control on ND response, this was in line with the accepted recommendation for use of animals for an experiment that state that six animals are the minimum animal welfare and statistically viable number that can be used (EMEA, 2001)
Forty eight (48) chicken were used for the seasonality study; 24 for each season, including the three age groups, while 72 were used for experiment to demonstrate effect of parasite control on ND response – 8 chicken per group, for the 8 groups used, and 8 birds for the initial assessment of parasite burden.
Study design
The study was carried out in 3 phases in line with the 3 study objectives given earlier, in Section1.1.2. Studies on antibody titer determinations and collection of questionnaire data (i.e. the first two objectives) were cross-sectional and sampling was purposive and convenient (based on reachable willing owners, regardless of the number of chicken kept; so long as the birds were kept on free-range system, had no history of ND, and no parasite control/treatment was exercised), study for the 3rd objective was longitudinal.
CHAPTER FOUR:
RESULTS
Data on poultry production systems, farmer demography and quality of eggs produced in the area
Management of poultry
All the farmers‟ interviewed kept local breed of chicken under the free range system. The day to day management of the poultry was carried out by women (88.0%) with assistance from the husbands and children (12.0%).
The farmers used more than one source of chicken for stocking; markets (64.7%) were the most common sources of the farmed chicken. Other sources included hatching from the flock (41.0%), purchase from neighbors (41.0%) and gifts from neighbors (5.0%) (Figure 4).
CHAPTER FIVE
DISCUSSION, CONCLUSIONS AND RECCOMENDATIONS
DISCUSSION
The study showed that domestic indigenous poultry production has a number of constraints with the major ones being diseases, parasites, lack of feed, predation and accidents, similar to what was reported by Njagi et al. (2010a) in the same area. ND was reported as the major disease constraint, as previously reported in other countries (Awan et al., 1994; Zeleke et al., 2005; Otim, 2005). Njagi et al. (2010a) also reported similar findings in the area five years back, indicating there has been no dynamic change. Factors such as management and handling of sick birds, disposal of carcasses, confinement, introduction of new birds from the market and wind have been associated as the major risk factors in ND outbreaks (Njagi et al. 2010a) and it has also been reported that live bird markets are a major source of infected poultry (Alexander, 1998). These practices are common in the area and had also been reported earlier by Njagi et al. (2010a), with sale and salvage of sick birds, throwing carcasses to the bush or feeding to dogs, introducing new entrants to flock without isolation, and confining birds of all ages together during certain times of the year being the main ones that could lead to spread and maintenance of the ND virus in the flock. Some farmers were observed to rear ducks together with chicken during the questionnaire interview and in so doing increasing the risk of ND outbreaks since ducks have been shown to shed ND without showing any clinical signs (Njagi et al., 2012). This indicates that minimal, if any, extension services are practiced in the area; hence the problems still remain the same.
Vaccination is not carried out by most village farmers as was the case during the study. Similar to previous report by Njagi (2008) and also by Otim (2005) in Uganda, this increases the risk of the birds coming down with ND, as vaccination is the only sure method of preventing ND (Alexander, 2003).
No farmer associated wild birds with ND outbreaks even though most homesteads had wild birds nesting and interacting with the chicken. Wild birds have been previously associated as possible sources of ND infections (Olabode et al., 1992).
The birds reared, in this study, had good productivity with the birds having between 2-3 clutches per year, each of 15-30 eggs. This observation agrees with that of Bebora et al. (2005) who compared indigenous hens with commercial layer birds brought for show exhibition at the Agricultural Society of Nigeria Show, Abuja, assessing their egg-laying capacity using pliability of their pubic bones. They found that some of the studied indigenous hens were very close to, while others had higher laying capabilities than the respective exotic ones. Lack of feed was quoted as a major factor affecting egg production, especially during the period between July and December; it resulted in drop in egg production, and was due to confinement of the birds in the planting season. This has not been reported in previous studies in the area. Most of the eggs produced were for home consumption, with a few being sold mainly in the local markets, in village shops, and directly to neighbors. If managed well, these birds could contribute and assist in improvement of nutrition and human health in rural population. The fact that chicken prices ranged from Kshs 50 for a chick to Kshs 800 for an adult cock, could easily contribute towards improving the economic status of the farmers; leading to poverty alleviation . Apart from income, chicken have socio-cultural importance to the community in ceremonies such as weddings, church events, family gatherings, baby showers and Christmas celebrations. Poultry also served as gift(s) to neighbors and as church offerings, thus, prevention of poultry losses is important in empowering the farmers and improving their social status. These socio-cultural practices can also be a source of spread for the virus, between homesteads during outbreaks. It is, therefore, important to educate the farmers on this, as part of the control measures for ND viral spread.
Overall the birds had high levels of antibody titer during both the wet and dry seasons, an indication of endemicity of the virus in the village chicken in Aba, as previously reported by Njagi et al. (2010b), who worked in the same area , Otim (2005) in Uganda and Zeleke et al. (2005) in Southern and Rift Valley districts in Ethiopia. Using Allan and Gough (1974) criterion which states that “a titer of 1:8 and above is generally accepted as indicative of specific immunity”, most birds had specific immunity meaning they had come in contact with the NDV. The wide range of NDV titer, shown in this study, may be due to natural infection which is known to produce higher antibody titers than vaccination (Luc et al., 1992). The continued hatching of chicks, which was the common re-stocking practice in this area, seemed to continuously provide susceptible chicken which could be infected by those that survived previous ND outbreak(s); an observation which was also reported by past researchers (Martin, 1992). This may have been the case during the wet season where the farmers reported an outbreak of a disease similar to Newcastle and serum samples from the birds showed high ND antibody titers; implying that chicken in this area got infected at different times producing a near cyclic pattern of disease, hence maintaining an endemic situation throughout the year (Otim, 2005; Njagi, 2008). Free range management system that allows the uninterrupted cycle of infection as the virus passes from one chicken to another may also be a cause of this endemicity, as suggested by Zeleke et al. (2005). The chicken may also acquire infection(s) from wild birds and in some instances from ducks, which some farmers kept together with chicken in Aba.
Ducks have been shown to harbor and shed the NDV without showing any clinical signs of the disease (Njagi, 2008). Methods of disposal of sick and dead birds such as throwing to the bush and feeding to dogs, practiced by some of the farmers in the area, which was also recorded by Njagi et al. (2010a) in the same area and Otim (2005) in Uganda, also aided in the spread of the disease and maintenance of the endemic status of the disease .
Both wet and dry seasons have been associated with ND outbreaks in Nigeria (Nyaga et al.,
1985). Start of wet season has been associated more with outbreaks (Jintana, 1987); in Vietnam (Nguyen, 1992) and Uganda (Mukiibi, 1992) higher seasonal incidence and severity of ND is reported in dry season. This is in line with Martin (1992) suggestion that outbreaks are often associated with change in season especially between wet and cold weather. In this study, ND outbreak may have occurred during the wet season hence the higher antibody titers during the wet than the dry season. This is supported by Awan et al., (1994)‟s conclusion that ND is associated with periods of stress, which could be due to change in climate and lowered resistance at the beginning of wet season, due to inadequate feed. The lowered resistance, in the current study was indicated by decrease in antibody titers in the dry season; coupled with increase in the number of susceptible birds. Concentration of HI antibodies has been reported to decline within 3-4 months of non-stimulation (Otim, 2005).
CONCLUSIONS
Based on the findings, it can be concluded that:
- Indigenous poultry are normally kept on free range system in the study area in Aba LGA. These birds play a significant role in the economic, social and cultural well being of the community.
- is the most significant constraint in poultry production in the region.
- The indigenous poultry have good productivity with good quality eggs.
- In all seasons birds have high titers, the antibodies tend to wane off during the dry season making the birds susceptible to introduction of velogenic strain of NDV.
- Parasite control results in improved immune response to ND; a comprehensive parasite treatment giving better results than partial treatments (for ecto- or endo-parasites only).
- If regular comprehensive parasite control is exercised birds will respond well to ND, hence be protected from the disease; they will be free from stress, caused by the parasites; and their productivity will improve. The resultant effect of this will be more income to the farmers, which will eventually translate to improved economy for the country as a whole. The farmers and their families will also get enough proteins, will be healthier, and hence be able to work better to build the country‟s economy.
- Albendazole at a dosage of 20 mg/kg body weight repeated monthly is both safe and effective in elimination of most helminths with the exception of Gongylonema inguivicolaand hence manufacture of r poultry formulation will be beneficial.
- Treatment, by dusting, of the ecto-parasites using a combination of sevin®and permethrin is effective against all the ecto-parasites. Application of the treatment on monthly basis should be recommended to avoid re-infection.
RECOMENDATIONS
- Vaccination is recommended during the start of dry season to maintain high levels of antibodies and prevent outbreaks, especially in chicks and adults.
- Education of flock owners on disease transmission and prevention and discouraging them from restocking their farms with chicken from the market.
- Treatment, by dusting, of the ecto-parasites using a combination of sevin®and pemethrin repeated monthly should be recommended for total control.
- Albendazole at a dosage of 20 mg/kg body weight repeated monthly by drenching should be recommended for use in helminth control.
- Total parasite control before ND should be recommended for effective immune response to the vaccine.
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