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TITLE OF THESIS The effect of experimentally induced yolk sac infection with Staphylococcus aureus on immune status of broiler chicks. INTRODUCTION The poultry industry in
Pakistan has made tremendous developments in the recent past, thereby greatly
contributing to fulfilling the protein needs of our ever-increasing human
population. Poultry meat has emerged as a good substitute of beef and mutton and
its importance can be judged from the fact that almost every family in rural
areas and every fifth family in urban areas are associated with poultry
production activities in one way or the other. The per capita availability of
poultry meat and egg per annum is still far below the required standards laid
down internationally. According to the economic survey 2001-2002, Pakistan
maintains an estimated 334.3 million day-old chicks, 18.4 million layers, 264.4
million broilers and 6.2 million breeding stock. The survey also estimated the
production of 266800 tons poultry meat and 4423 million eggs for the year
2001-2002 (Anonymous, 2002). In addition to its primary role of meeting the
rapidly increasing demand of animal protein in the country, it has also
significantly contributed to the national GDP. In recent years, growth of the
Pakistan poultry industry has considerably slowed down, mainly due to worsening
disease situation and increasing average mortality in both layer and broiler
flocks. Amongst
the various factors threatening poultry industry of Pakistan, bacterial disease
problems carry great significance especially causing early chick mortality in
poultry and cause considerable economic loss (Anjum, 1990). The first two weeks
of age are very important in the life of a broiler chick as about
30-50% mortality occurs in this period. Major problems during this period
are omphalitis, brooder pneumonia, avian encephalomyelitis, spiking mortality,
dehydration, ammonia burns and pullorum disease (Charlton, 1996). The most
prevalent and the commonest cause of early chick mortality in Pakistan is yolk
sac infection. Infection of the yolk sac and navel are responsible for the
majority of deaths in chicks up to 3 days after hatching. Peak mortality occurs
within 2 or 3 days after hatching and then suddenly declines. Mortality varies
from 10-30% (Anjum, 1997). There are many causes of yolk sac infection, among
which the infections by Escherichia coli, salmonella, staphylococcus,
pseudomonas, Bacillus cereus, enterococci, clostridia and proteus
carry the importance. These bacteria invade the host via the unhealed navel or
blood stream or through shell penetration into yolk before hatching (Anonymous,
2000). The nutrient substances and
immunoglobulins present in the yolk sac are used by the chick during first few
days of development. Yolk sac is also an important mean of providing passive
immunity. Passive immunity present in the yolk represents defenses that are
determined from maternal experiences (Vieira and Moran, 1999). The transference
of antibodies has been demonstrated by Box et al. (1969) and Stone et
al. (1992). Immunoglobulins are serum proteins and play an important role in
immune status (Tizard, 1987). Infections alter protein structure and thus may
lower the immune status of animals (Hegazi, 1990; Segarra et al., 1991). Because
of the importance of maternal immunity and potential of bacterial invasion into
the yolk sac to alter protein structures, yolk sac infection adversely affecting
passive protection and serum proteins is a concern. Comprehensive work on
various aspects of yolk sac infection including incidence, causative organisms,
experimental infection and pathology has been undertaken by several workers.
However, a little work appears to have been done on yolk sac infection from
standpoint of its effect on the immunity. The present project has been taken in
hand with a view to study the effect of experimentally induced yolk sac
infection with Staphylococcus aureus on immune status of broiler chicks.
It is hoped that the findings of this study would go a long way in
understating the infection of yolk sac with Staphylococcus aureus and its
effects on immune status of broiler chicks. REVIEW OF LITERATURE This chapter will be available soon. MATERIALS & METHODS This chapter will be available soon. RESULT This chapter will be available soon. DISCUSSION Omphalitis
or yolk sac infection occurs frequently in commercial poultry. The most
prevalent bacterium causing yolk sac infection is Escherichia coli
(Williams and Gains, 1942; Sudhir and Munro, 1969; Bhatia et al., 1971a;
Bhatia et al., 1971b; Baig, 1976; Zahdeh et al., 1984; Utomo et
al., 1990; Rudy, 1991; Choudhury et al., 1993; Deeming, 1995; Anjum,
1997; Anonymous, 2000; Rossi et al., 2000). Besides E. coli, Staphylococcus
aureus is the next most important bacterium associated with yolk sac
infection (Volkmar, 1929; Williams and Gains, 1942; Sudhir and Munro, 1969;
Bhatia et al., 1971a; Bhatia et al. 1971b; Baig, 1976; Terzolo,
1978; Zahdeh et al., 1984; Utomo et al., 1990; Rudy, 1991; Skeeles,
1991; Choudhury et al., 1993; Deeming, 1995; Anjum, 1997; Anonymous,
2000; Rossi et al., 2000). The
infected yolks were large in size, having yellowish brown and green to yellowish
red appearances, offensive pungent smell and watery to caseous consistency.
Brandly (1932), Harry (1957), Bhatia et al. (1970), William (1975),
Jordan (1990), Skeeles (1991), Sainsbury (1992), Rehman et al. (1996) and
Anjum (1997) reported similar observations. Yolk
sac weight/body weight ratio was higher in infected group as compared to control
group. Similar findings are reported by Sander et al. (1998) and Khan
(2002). This observation can be explained as the weight of the unabsorbed yolk
was higher and body weight was lower in chicks infected with Staphylococcus
aureus than that of control chicks. Deeming (1995), Sander et al.
(1998) and Khan (2002) observed high yolk sac weight in chicks infected with
yolk sac infection. Lower body weight in infected chicks was reported by Khan
(2002). Haemagglutination
inhibition titres of serum and yolk against Newcastle Disease Virus (NDV)
decreased with age being highest at day 3 and lowest at day 9. These results are
favoured by the findings of Saeed et al. (1988) who reported that HI
titres were (log mean 27) on first day, (log mean 26) on 5th day and (log mean
25) on 10th day of age. Results are also in accordance
with the findings of Kaleta (1972), Miyamoto et al. (1977) and Mitra et
al. (1998). HI antibody titres of serum against NDV were significantly lower
in infected chicks than the control chicks. Sander et al. (1998) also
reported that the geometric mean serum titre (log2) for Newcastle
disease antibody was significantly lower in chicks infected with Streptococcus
faecalis than in control chicks. This observation may be justified as in
infected chicks maternal antibodies against NDV are not absorbed from the yolk
and their concentration in serum decreases. On the other hand HI antibody titres
of unabsorbed yolk samples against NDV were significantly higher in infected
group as compared to yolks of control group. Low serum and high yolk antibody
titre may be justified as bacterial contamination of yolk sac decreased passive
antibodies absorption either by protein alteration, binding or decrease in the
ability of yolk sac membrane to absorb proteins (Sander et al., 1998). Youssef et al. (1988),
JengShang et al. (1999) and Sadaf (1999) used SDS-PAGE for serum protein
analysis. This technique was used to evaluate the effect of yolk sac infection
on serum protein fractions, which could be used in diagnosis of immune status of
the chicks. Campbell (1992) reported that among serum protein electrophoresis,
SDS-PAGE is a powerful and versatile technique and could be used to study the
serum protein contents. The mean percent area covered by serum protein fractions
of molecular weights 126, 112, 89, 71, 64, 50, 25 and 22 kDa was lower and of
molecular weights 45 and 20 kDa was higher in infected than in control group
while mean percent area covered by protein fractions of molecular weights 56, 32
and 28 kDa was variable. On day 3, the infected group showed decreased protein
fractions of molecular weight 126 (hepatoglobin), 71 (alpha-fetoprotein), 32
(alpha-acid glycoprotein) and 28 kDa, and increased protein fractions of
molecular weight 56 (prealbumin) and 20 kDa as compared to control group. On day
5, protein fractions of molecular weight 112 (hepatoglobin), 89 (transferrin),
56 (prealbumin), 32 (alpha-acid glycoprotein), 25 and 22 kDa were decreased
while protein fraction of molecular weight 28 kDa was increased in infected
group as compared to the control group. On day 7, the infected group showed
decreased protein fractions of molecular weight 112 (hepatoglobin), 50 (prealbumin)
and 25 kDa and increased protein fractions of molecular weight 45 and 32 kDa
(alpha-acid glycoprotein) than control group. On day 9, the infected group
showed decreased protein fractions of molecular weight 112 (hepatoglobin), 64
(albumin), 56 (prealbumin) and 25 kDa and increased protein fractions of
molecular weight 28 kDa as compared to control group. From the above results it
can be inferred that transferrin and albumin values were slightly decreased in
infected group. Youssef et al. (1988) reported a decrease in albumin
value after S/C infection with Salmonella arizonae. Pearson (1990)
reported decreased values of albumin in horses with parasitic infestation,
chronic infection, inflammation and neoplasm. Jain (1993) reported that serum
transferrin decreased in acute and chronic infections and leukemia. In this
study, infected group showed decreased hepatoglobin concentration but this
finding is not in line with the findings of Kent and Goodall (1991) who reported
that hepatoglobin concentrations were elevated in infections and inflammatory
conditions in horses. This difference might be due to species variation. In our
results, the prealbumin values were elevated in infected group initially and
then decreased. Youssef et al. (1988) reported a significant increase in
pre-albumin values after S/C infection with Salmonella arizonae. Jain
(1993) reported that concentration of prealbumin was elevated with acute
infections, laminitis and malignant tumours. Such decrease in certain proteins
and increase in others is in partial agreement with the findings of Ching and
Yeh (1992) who reported that in acute heat stress in chickens and broilers the
serum proteins of 30, 40, 83 and 94 kDa increased but not those of 24, 70 and 90
kDa. Tohjo et al. (1995) studied polyacrylamide gel electrophoretic
pattern of chicken serum in acute inflammation and reported that the
electrophoretic patterns were divided in to 21 segments but only two of these
segments increased markedly. Sefer et al. (1999) reported that in T-2
toxin treated chicks, alpha and gamma globulin concentration increased, albumin
concentration decreased and albumin: globulin ratio narrowed. It
is therefore concluded that yolk sac infection with Staphylococcus aureus
not only increases yolk sac weight/body weight ratio with marked pathological
changes in yolk but also results in low immune status of chicks which is the
consequence of decreased maternal antibody absorption and altered serum protein
fractions.
SUMMARY The
present project was carried out to study the effect of experimentally induced
yolk sac infection with Staphylococcus aureus on immune status of broiler
chicks. For this purpose one hundred day-old chicks were procured from local
market and were randomly divided into two groups, A and B having fifty chicks
each. Confirmed pathogenic isolate of Staphylococcus aureus was
inoculated into the yolk of each chick of group A while group B acted as
control. Ten chicks from each group were slaughtered at interval of 48 hours
i.e. on 3rd, 5th, 7th, and 9th day
of the experiment and serum and yolk were collected. Experimental parameters
included pathological examination of yolk sac, yolk sac weight/body weight
ratio, antibody titres against Newcastle disease virus (NDV) in serum and yolk
and analysis of fractional serum proteins. Results
showed that yolk sac weight/body weight ratio was higher in treatment group than
in control group. Marked pathological changes (abnormal colour, consistency and
odour) were also observed in unabsorbed yolks of the infected group. Geometric
mean titres of maternal antibodies against NDV were significantly lower in serum
while higher in yolk of the infected group as compared to control one. Sodium
dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) was used for
serum protein analysis and percent area covered by each protein fraction was
calculated. The percent area covered by most fractions of serum protein was
lower in infected chicks than the control chicks. It
is therefore concluded that experimental yolk sac infection with Staphylococcus
aureus leads to decreased maternal antibodies absorption from infected yolks
and altered serum proteins indicating decline in the immunity of the chicks. LITERATURE
CITED This chapter will be available soon.
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