Poultry diseases and treatment
Dr. Mujeeb Ather Asst. Director (Pathologist)
Veterinary Biological Research Institute, Hyderabad .
MEREK’S DISEASE:
- MEREK’S DISEASE IS CAUSED BY A CELL ASSOCIATED
HERPES VIRUS FOR WHICH THREE SEROTYPES HAVE BEEN DEACRIBED.
- MAREK’S CHALLENGE HAS INCREASED SIGNIFICANTLY
DURING THE PAST SEVERAL YEARS.
TRANSMISSION:
- DIRECT OR INDIRECT CONTACT BETWEEN BIRDS AFFCTS VIRUS
SPREAD, APPARENTLY BY THE AIR BORNE ROUTE.
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- NO VERTICAL TRANMISSION OF MDV.
SYMPTOMS:
- INCUBATION PERIOD IS DIFFICULT TO DETERMINE UNDER FILED
CONDITIONS, IN EXEPERIMENTAL CASES IT IS APPROXIMATELY
2 WEEKS.
- MOST SERIOUS CASES BEGIN AFTER THE 8 TH OR 9 TH WEEK
WHILE OUT BREAKS SOMETIMES OCCUP.
- MORBIDITY AND MORTALITY IS EQUAL.
- PRIOR TO USE OF VACCINES, LOSSES IN AFFECTED FLOCKS
WERE ESTIMATED TO RANGE FROM A FEW BIRDS TO 25 OR 30% AND
OCCASSIONALLY AS HIGH AS 60%.
- PROGRESSIVE PARESIS AND LATER COMPLETE PARALYSIS OF
ONE OR MORE OF THE EXTREMITIES.
- A CHARACTERISTIC ATTRIBUTE IS THAT IN WHICH THE BIRD
HAS ONE LEG STRERCHED FORWARD AND THE OTHER BACK AS A RESULT
OF UNILATERAL PARALYSIS OF THE LEG. (SQUATTING POSITION).
- NON SPECIFIC SIGNS SUCH AS WEIGHT LOSS, PALENESS AND
DIARRHOEA MAY BE OBSERVED.
- AFTER THE DISEASE APPEARS, MORTALITY BUILDS GRADUALLY
AND GENERALLY PERSISTS FOR 4-10 WEEKS.
GROSS LESIONS:
- ENLARGEMENT OF THE SCIATIC AND BRACHIAL NERVES WITH LOSS
OF CROSS-STRIATIONS, GRAY OR YELLOW DISCOLOURATION.
- LYMPHOID TUMORS OCCUR IN ONE OR MORE OF VARITY OF ORGANS.
NODULAR TUMOR LIKE GROWTHS ARE FOUND WITHIN AND EXTENDING
FROM THE PARENCHYMA OF THE ORGAN. THESE ARE FIRM AND SMOOTH
ON CUTTING.
Nodular tumors in the liver
DIAGNOSIS:
- SYMPTOMS AND GROSS LESIONS
- HISTOPATHOLOGICAL STUDIES
- ISOLATION OF THE VIRUS
PREVENTION AND CONTROL :
- STRICT BIO-SECURITY : KOHRSOLIN-TH SPARY
- VACCINATION
- THE STRAIN OF VACCINE AND/OR COMBINTIONS USED VARY ACCORDING
TO CONDITIONS OF THE FIELD CHALLENGE.
IT HAS ALSO BECOME COMMON PRACTICE TO REVACCINATE DAY
OLD CHICKS UPON RECEIPT AT THEIR DESTINATION. THIS
IS REPORTED TO BE VERY EFFECTIVE IN CONTROL OF MAREK’S
DISEASE.
- RECENTLY, MDV FIELD STRAINS TROPISMS AND INCREASED CONDEMNATIONS
AND/OR MORTALITY HAVE BEEN OBSERVED.
- THE INCREASE IN MORTALITY CAUSE CONCERN BECAUSE APPARENT
LOSS OR EFFICACY OF THE MOST COMMONLY USED
VACCINE (HVT AND SB-1). THIS SUGGESTS THAT A NEW STRAIN
OR PATHOTYPE OF VV MDV CAPABLE OF OVER RIDING CURRENT CONTROL
MEASURES.
- THE FIRST VACCINE PRODUCED AND UTILIZED WAS HERPES VIRUS
OF TURKEYS (HVT). FOR ATLEAST A DECADE, THIS
VACCINE PROVED TO BE HIGHLY EFFICACIOUS AS A MONOVALENT
PRODUCT.
- DURING THE LATE 1970 S’ AND EARLY 1980 S’ A
SUBSTANTIAL INCREASE IN MD OUTBREAKS WERE REPORTED.
FOLLOWING THE INTRODUCTION OF THE SEROTYPE 2, SB-1 VACCINE
WHICH WAS USED IN A BIVALENT COMBINATION WITH HVT, MORTALITY
DECREASED UNTIL THE MID 1980 S’
- IN 1992 THE INCIDENCE AGAIN INCREASED AND THIS TREND
CONTINUED TILL TODAY.
- THIS INCREASE INCIDENCE OF MD IS THE RESULT OF EMERGING
VIRUS STRAINS THAT APPER TO REPLICATE MORE
EFFICIENTLY AND INDUCE TUMORS THAT ARE PARTICULARLY INVASIVE
AND FAST GROWING.
- THE MOST EFFICACIOUS MONOVALENT VAVVINE IS RISPEN STRAIN
(CV1-988) WITH THE COMBINATION OF THE SAME
CV1-9DD AND HVT BEING THE MOST SUCCESSFUL.
SL.NO. NAME OF VACCINE PERCENTAGE PROTECTION
1 ST DAY POST VACC 5 TH DAY POST VACC
1 CVI-988 83 96
2 CVI-988+HVT 93 99
3 CVI-988+HVT+SB-1 78 95
4 HVT+SB-1 72 84
5 HVT+301-B 41 92
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