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Retrospective investigation of poultry mortality in Tsirang- a report

Dr. Rinzin Pem

Sr. VO, RLDC Wangdue

I. Background

Given the large number of mortality in eight poultry farms in Gosaling geog and two

farms in Tsholingkhar geog over a period of one week and with all the affected farmers

seeking for free replacement stock from Dzongkhag, RLDC Wangdue was intimated and

hence the need to carry out retrospective disease outbreak investigation in the affected

geogs was felt.

DVH Tsirang investigated and closely monitored the outbreak since day one of its

occurrence. Although various samples and relevant data were collected during the

outbreak period, no definite diagnosis has been made. Owing to this, the retrospective

investigation was mainly aimed to validate their findings and find out the cause and

possible source of the outbreak.

II. Retrospective investigation methodology

1. Review the report on disease outbreak investigation conducted by DVH Tsirang and

information gathered from the DVH Tsirang investigation team.

2. Visit affected poultry farms and interview the farm owners on events related to disease

occurrence.

3. Collect relevant samples for further laboratory analysis.

III. History

DVH Tsirang received reports of increased mortality in young poultry birds in a total of

eight layer farms located at Pemathang and Zomlingzor village in Gosaling geog and

Drupchugang and Lower Tsholingkhar villages of Tsholingkhar geog on 31st May 2014.

The incidences were reported by respective geog livestock in-charges. A team from DVH

immediately visited the affected farms for detail investigation and to institute appropriate

control measures.

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During the investigation, it was found that on 30th

May 2014, the owners of most of the

affected farms reported increased mortality to the geog livestock office. Appropriate

prevention and control measures were taken by the geog officials in both the geogs and

the outbreak incidences was then reported to DVH for further timely intervention.

Control and prevention measures instituted by Geog extension centre and DVH

Tsirang

Isolation of sick and affected birds from apparently normal birds.

Affected and in-contact birds treated with Tetracycline Hydrochloride

powder, Diaveridine and sulfaquinoxaline/ other coccidiostats and also feed

supplements (minerals and vitamins).

Owners were advised to thoroughly clean and disinfect the feeders and

waterers in the affected shed.

The carcasses of dead birds were disposed off following strict zoo sanitary

measures.

Owners were advised to change the litter in the contaminated shed and to

leave it vacant for a minimum of 21 days during which thorough cleaning and

disinfection to be done.

Owners advised to heighten bio security measures in the farms and prevent

further spread.

Affected farms were timely monitoring by Geog extension centre and DVH

Tsirang to control the infection and prevent new cases.

IV. Findings

a. Source of the chicks

The layer day old chicks were sourced from Satara Hatchery, an NPDC

contracted hatchery at Juprey at the rate of Nu. 30 per chick. Most of the farmers

lifted the chicks from the hatchery in hired vehicles.

b. Vaccination status

During the time of investigation, the vaccination status of the affected flock has

been recorded as vaccinated against Marek’s disease (done at the hatchery

immediately after hatching), ND (first dose on day 7) and IBD (new schedule

followed: first dose on day 10)

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c. Details of affected flocks

Sl.

No.

Name of the

poultry farmer

Village Geog Age

group

affected

(days)

Total

stock

Mortality

(number)

Mortality

(%)

1 Dewan Pradhan Pemathang Gosaling 23 1053 500 47.5

2 Diliram Wakhley Pemathang Gosaling 23 1300 500 38.5

3 Tshering Tamang Pemathang Gosaling 23 300 150 50

4 Goma Das Thapa Pemathang Gosaling 28 300 180 60

5 Sonam Yangdon Pemathang Gosaling 28 250 20 8

5 Til Bahadur Nepal Zomlingzor Gosaling 23 318 200 62.9

6 Bola Nath Sutar Zomlingzor Gosaling 38 300 150 50

7 Hatu Chuwan Zomlingzor Gosaling 23 300 190 63.3

8 Sonam Tshering Zomlingzor Gosaling 28 250 230 92

9 Purna Bdr. Subba Drupchugang Tsholingkhar 15 500 52 10.4

10 Santa lal Monger Tsholingkhar

Maed

Tsholingkhar 23 500 200 40

Total 5371 2372 44.2%

d. Temporal pattern of the disease

On interviewing the affected farmers, it was found that the first case and first

death in the geog occurred on 30th

May 2014 with peak mortality on the second

and third day after the first death. The deaths in most of the farms occurred

around the same time and the whole outbreak lasted for 5-6 days. By the end of

first week of June, the outbreak has completely subsided. Except for the total

number of deaths and the verbal accounts of increased deaths on the second and

third day, there is no records of daily mortality rates.

During the period of outbreak, change in weather patterns with cycles of intense

sun and heavy rain was reported in Tsirang. Prior to the outbreak period, there

were no reports of introduction of new birds or equipments in the farms. Some of

the affected farmers claim that in their almost a decade venture into poultry

farming, such a disease with acute intensity wiping off almost half of their flock

was encountered for the first time.

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e. Symptoms (as narrated by owners and investigation team members of DVH

Tsirang)

Depression, off feed, vent soiled with whitish droppings/bloody droppings in

some, ruffled feathers, huddling in one place, and in few, paralysis was also

noticed. (Picture courtesy: Rinzin Dorji, Lab Tech, DVH Tsirang)

Figures showing birds with droopiness, ruffled feathers and huddling

f. Post mortem lesions observed

i. External examination

The carcass was found to be weak and dehydrated, ruffled feathers, vent soiled

with white diarrhoeic faeces and in some with hints of blood.

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Figure showing weak and dehydrated carcasses

ii. Internal examination

Marked haemorrhages in the thigh muscle and in some birds,

haemorrhages were also seen in the pectoral muscles.

Figure showing marked haemorrhages in thigh muscles

Intestines congested in most of the birds with caecal tonsils swollen and

filled with bloody contents.

Bursa swollen and filled with cheesy exudates.

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g. Laboratory samples collected and analysed

Sl.

No.

Type of

samples

No. of

samples

Type of test Laboratory

Findings

Remarks

1 Faecal

droppings

40 Direct/Sedimentation

/Stoll/Floatation

techniques

500-1200 OPG

coccidian oocyst

detected

Conducted at DVH

Tsirang

2 Feed

sample

3 Sample referred to

RLDC Wangdue for

Qualitative Aflatoxin

testing

Weak positive to

aflatoxin

Conducted at RLDC

Wangdue

3 Tracheal/Cl

oacal swabs

30 Rapid Antigen

Detection test against

Avian Influenza

virus

Negative to

Influenza A

Carried out in the

field

4 Organ

Impression

smear

10 Direct Gram

staining/Leishman/G

eimsa staining

No pathogenic

bacteria detected

Conducted at DVH

Tsirang

5 HP samples

(collected

on 30.05.14

& 02.06.14)

2 HP examination Laboratory

results awaited

Sample referred to

NCAH on 22nd

June

2014

6 Serum

samples

(collected

from

remaining

birds in the

flock on

22.06.14)

7 ELISA (antibody

detection)

Laboratory

results awaited

Sample referred to

NCAH on 22nd

June

2014

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Figure showing negative AIV antigen Figure showing mouldy lumps in feed

in the affected birds

h. Similarities between the affected farms

1. The layer DOCs in all the farms were sourced from Satara Hatchery and

transported to Tsirang in hired vehicles separately.

2. No loss of DOCs/birds from the day of lifting from hatchery till the disease

outbreak occurrence.

3. No history of introduction of new birds/equipments/fomites into the farm.

4. The affected bird flocks were of similar age group, with a difference of a week or

two between some flocks.

5. Deep litter system practiced in all farms.

6. Potassium permanganate or Kohrsolin solutions used as foot dip in most of the

farms.

7. Commercial feed (Karma feed) used by all the farms

8. All in all out management system not practiced. Most farms had broiler birds,

adult layer birds in adjoining sheds.

i. Differences between the affected farms

1. No two affected farms were in close proximity despite the occurrence of disease

outbreak at around the same time. In addition, there is no history of introduction

of new birds/equipments/fomites into any of the farms.

2. Level of bio-security differed between the farms. Eg. No proper foot dip tank in

some farms and the frequency of change of solutions variable (mostly done at

owner’s convenience!)

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j. Diagnosis

Based on the salient post mortem lesions, age of the affected flock (3-5 weeks), acute

and infectious nature of disease spread, mortality pattern, the outbreak has been

provisionally diagnosed as Acute Infectious Bursal Disease Outbreak (IBD).

Concurrent infestations with coccidia sps with oocysts ranging from 500-1200 OPG

in the affected birds could have further worsened the disease outbreak situation. The

sudden change in weather conditions could have triggered suspected IBD outbreak

and besides the chicks in majority of the farms were nearing their first IBD vaccine

booster dose.

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V. Recommendations

1. Bio-security practices needs to be improved in most of the affected farms to prevent

future disease outbreaks. For their strict compliance, there is an immediate need to

educate the poultry farmers on the bio-security guideline for poultry farms and make it as

a basis for regulation of the poultry farms.

2. Proper record keeping needs to be practiced by the poultry farmers to record all the

happenings in the farm. Due to lack of proper recording, except for the number of total

deaths, no data on the day wise morbidity and mortality could be collected for this

outbreak.

3. Regulatory guidelines for in-country source of live poultry (hatcheries) should be

developed to regulate and ensure good management practices to prevent introduction of

disease pathogen at the source.

4. Since no other source of the infection could be established and as the affected birds

were sourced from the recent IBD outbreak area (Juprey) around 9th

May 2014, there is a

strong assumption given the stable nature of the virus that this outbreak could be the

spillover infection from the April 2014 outbreak in Sarpang. If this is assumptions turn

out to be true, proper SOPs for sourcing/transportation of DOCs/movement control

measures in events of disease outbreak in the locality of hatchery should be adopted to

prevent future inter Dzongkhag spread of poultry infection of similar nature. However, a

thorough study needs to be carried out to see whether the outbreaks at Sarpang and

Tsirang are related.

VI. Limitations

1. Since this investigation is of retrospective nature, there is possibility of recall bias and

misinterpretation of the events that occurred during the outbreak. However, efforts have

been made to capture the true events as best as possible.

2. Since the outbreak had already subsided during the time of visit, the provisional

diagnosis has been reached after assimilating verbal accounts of the farmers, information

obtained from DVH staffs and after reviewing the outbreak investigation report prepared

by DVH Tsirang team.

3. The serum samples were collected from remaining birds in the affected flock on 22nd

of June 2014 and these birds can be either be uninfected or those that have recovered

from the infection.