Seroprevalence and Haematological Studies of Some Wild and Semi-Domesticated Birds Naturally Infected With Avian Pox Virus in Zaria, Nigeria

Introduction

Birds serve numerous functions in the economy of many nations in terms of meat and egg supply apart from their value as a source of income among peasant (Nuru, 1992).In Nigerian, poultry consist of about 10 million local chicken, 45 million guinea fowls, and 1 million each of turkeys, pigeon and ducks. It is estimated that poultry supplied about 10% of the total meat for human consumption. (Newathe and Lamorde, 1982; Oladele et al., 2001). At the moment, no information on the estimated number of wild birds in Nigeria. Guinea fowls and pigeons are semi-domesticated birds that are kept in towns and villages; and are also abundant in the wild in African continent, (Oladele et al., 2005). Domestic and wild birds have been documented to be susceptible to some viral diseases. Conventional disease control programmes are easier to supply to birds on organized farms, but are very difficult where movements are unrestricted. It is these unrestricted domestic and wild birds that maintain the virulent viruses and bacteria in circulation, challenging continuously birds on the commercial poultry farm, (Newathe and Lamorde, 1982; Olayemi and Fagbohun, 2006). Avian pox, a viral disease of birds is caused by one of the larger viruses of the pox virus group. This relatively slow-developing disease is characterized in birds by discrete, proliferative lesion on the skin of the toes, legs or head and or mucous membranes of the mouth and upper respiratory tract. Systemic infections may also occur in birds, (Tripathy and Reed, 2003). Avian pox is comparable to the pox infections of wild mammals (Robinson and Kerr, 2001), domestic mammals (for example, sheep sore-mouth, swine poxes and those of man (small pox). The subgroup of avipox viruses contains a number of species and strains that vary in their pathogenicity and host specificity, (van Riper and Forrester, 2007). The widespread avian disease has been found in a large number of bird families, with Phasianidae, Emberizidae seeming more susceptible than others. In most birds, avian pox infections are mild and rarely result in death. However, when lesions are on the eyelids or mucous membranes of the oral and or respiratory cavities, mortality can be high, (Tripathy et al., 2000). As with many other diseases that are density dependent, avian pox transmission is enhanced with increasing vector and or host densities, (Vargas, 1987; van Riper et al., 2002). In the wild, the warmer and mesic regions of the world support more potential vectors, thus in these areas the prevalence of avian pox is higher, particularly in flocking wild birds (Annuar et al., 1983; van Riper and Forrester, 2007). Rural poultry production in Nigeria is faced with problems of improper management practices, such as lack of vaccination and routine treatment or deworming. This usually results in a serious problem that leads to decrease in egg production, low quality of meat and poor productivity performance by the bird, which could make the birds more susceptible to avian pox infections, (Olayemi et al., 2002).To the best of our knowledge, there is no information on seroprevalence and haematological studies of some wild and semi-domesticated birds naturally infected with avian pox virusin Zaria, Northern, Nigeria. Therefore it is pertinent to determine the seroprevalence and haematological parameters of these important avian species in relation to avian pox, which is equally an important disease.

Materials and methods

Study Area

The experiment was conducted in Zaria, Northern, Nigerian, which is located in the Northern Guinea Savannah zone (11o 10 N, 07O 38’E). Trees and grasses characterize the vegetation of this zone with average rainfall, ranging from 1000mm to 1250mm, and temperature of 17oC to 33oC (Sa’id et al., 1994; Oladele et al.,2003). Different species of domestic and wild birds have been identified in this geographical zone (Oladele et al., 2012).

Experimental Birds

A total of 160 birds consisting of 40 helmeted Guinea fowls, 20 domestic pigeons, 10 Speckled pigeons, 10 Mourning Collar doves, 10 Laughing doves, 10 Village weavers, 10 Cut throat fire finches, 10 Cattle Egrets, 10 Rose-ringed parakeets, 10 African silver billed, 10 Red-Billed Quelea, 10 Senegal parrots were used for the purpose of the study. Both the wild and semi-domesticated birds were sampled from Zaria metropolis, Kaduna State, Nigeria.

Collection of Blood and analysis

Two to five milliliters of blood were collected from each bird using sterile plastic disposable 5ml syringe and 25 x 7 mm gauge needle via brachial vein. Half of the blood was put in an EDTA bottle and the remaining half of the blood from each bird was allowed to coagulate, then centrifuged at 313 xg for 15minutes to obtain serum and stored at - 20oC until required. PCV, haemoglobin, differential cell count and total protein were performed according to standard procedures.

Serological Procedure

The agar-gel precipitation test was carried out on the serum samples for the detection of Avian Pox antibodies using the methods described by Dhinakar Raj et al. (1995). Agar-gel precipitation test was carried out using immuno-diffusion plate at 7.2±0.1 pH and the template was incubated at 37oC in humid chamber to prevent drying of the agar and read at 24, 48, and 72 hour interval under diffused light. The result was compared between the positive and the negative test serum. Positive serum samples show a line of precipitin between the serum antigens well while the negative serum samples show no line of precipitation.

Serological Procedure

Results

Ninety per cent of the serum samples obtained from Speckled pigeons were positive for antibodies to avian pox virus, 20 (100 %) serum samples obtained from domestic pigeons was positive, while 8 (80 %) serum samples out of 10 obtained from Mourning Collar doves were also positive, 10 (100 %) serum samples out of the10 obtained from Laughing doves were positive for avian pox virus antibodies, 7 (70 %) were positive from the 10 sera obtained from Village weavers, while 8 (80 %) were positive from the 10 sera.

Obtained from Cut throat fire finches. Nine (90 %) serum samples out of 10 obtained from Cattle Egrets were positive, while out of40 serum samples obtained from helmeted guinea fowls, 37 (70 %) tested positive. On the other hand, 10 (100 %) sera obtained from Rose-ringed Parakeet all tested positive, while out of 10 sera obtained from African silver billed 9 (90 %) were positive. All the 10 (100 %) sera obtained from Senegal parrots were positive, while only 8 (80 %) were positive out of the 10 sera obtained from Red-billed quelea (Fig. 1).

Seroprevalence and Haematological Studies of Some Wild and Semi-Domesticated Birds Naturally Infected With Avian Pox Virus in Zaria, Nigeria - Image 1

Fig.1: Seroprevalence of avian pox virus antibodies of some wild and semi-domesticated birds.

Key: SP-Speckled Pigeon, CTFF-Cut Throat Fire Finch, SPA-Senegal Parrot, DP-Domestic Pigeon, CE-Cattle Egret, RBQ-Red-Billed Quelea, MCD-Mourning Collar Dove, HGF-Helmented Guinea Fowl, LD-Laughing Dove RRPRose-ringed Parakeet, VW-Village Weaver, ASB-Africa Silver Billed.

The mean values for PCV, Hb, RBC and TWBC of birds that were positive to avian pox virus antibodies and those without avian pox antibodies are shown in Table 1. The mean value for PCV of 40.0±1.3% obtained from Helmeted Guinea fowl that were positive to avian pox antibodies is lower than the mean value of 42.0±3.6% recorded from the same species of bird that were negative to avian pox antibodies. On the other hand, the mean values of 3.30±0.3x1012/L of RBC obtained from Senegal Parrot that were positive to avian pox virus antibody is higher than the mean value of 2.80±1.4x1012/L of RBC recorded from the same species of birds that were negative to avian pox virus antibodies (Table 1). Table 2, shows the mean differential absolute leucocyte count and total plasma protein of birds that were positive to avian pox virus antibodies and birds that were negative to avian pox antibodies. The mean heterophil values of 0.2±0.1x109/L obtained from Cut throat Fire Finch that were positive to avian pox virus antibodies is lower than the mean heterophil value of 0.9±0.04x109/L recorded from the species of birds that were negative to avian pox antibodies. Similarly, the mean value for basophil (0.02±0.0x109/L) obtained from Mourning Collar Dove that were positive to avian pox virus antibody was lower than the value of 0.05±0.03x109/L recorded from the same species that were negative to avian pox antibodies (Table 2).

Table 1: Comparative values of blood cell indices between positive and negative cases of avian pox antibodies of some wild and semi-domesticated birds.

Table 2: Comparative values of differential leucocyte count and total plasma protein between positive and negative cases of avian pox antibodies of some wild and semi-domesticated birds.

Discussion

The results of this study demonstrated serological evidence of avian pox virus (APV) antibodies in all the wild and semi-domesticated birds sampled in this study. This finding agrees with the report of Clements (2000) that if the birds are adequately exposed to APV they are susceptible to one or more of the avian pox virus strains. This shows that these species of bird in this study were already exposed to APV prior to sampling and hence, could be a source of infection to commercial poultry. Most of the sampled birds, such as pigeon’s, doves, weaver birds and guinea fowls that were positive for APV antibodies were those usually found around human habitations and commercial poultry houses. It is, therefore, important to note that they can serve as means of transmission of avian pox infection as they interact with the domestic fowls. This could be possible through contamination of feed and water of domestic birds with their faeces or scabs formation or direct contact with the susceptible host and mechanical means via biting insects. Since no clinical signs or lesions of avian pox were found in all the birds where APV antibodies were detected, these wild birds can serve as reservoirs of avian pox infection, and consequently, shed the virus in and around poultry houses, thereby becoming threat to poultry production in Zaria, Nigeria. The differences observed in some of the parameters (Lymphocyte, heterophil, total protein, monocyte) in this presented study may be due immunological response to bring the infection the level of sterile immunity. The normal PCV values for many bird species ranges between 29% and 58.5% (Thrall, 2004). Most of the birds sampled in this study had values within the normal range values irrespective of whether they were positive or negative for avian pox virus antibodies. This finding agrees with the report of Forrester and Spalding (2003). The lowest TP values of 2.07±0.2g/dl obtained in this study from Village Weaver (Ploceuscycullatu) is less than the lower value of 3.00g/dl established for both apparently healthy wild and domestic birds, while the highest value of 5.3±.2g/dl obtained in this study from Laughing dove (Streptopeliasenegalensis) were within the normal range of 6.00g/dl established for wild and domestic birds (Campbell and Coles, 1986).

Conclusion

This study demonstrated the serologic evidence of avian pox virus antibodies in some wild and semi-domesticated birds in Zaria, Nigeria. The predominant leukocytes of the sampled birds in this study were the lymphocytes and heterophils, accounting for up to 95% or more of the WBC on the average.

This article was originally published in African Journal of Cellular Pathology 8: 15-20 (2017). http://www.ajcpath.com.