Cook, Raymond W.

Texas A&M University

B-I(IOB
Texas Agricultural Extension Service
Infectious
Laryngotracheitis
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Raymond TV rook
Extension Veterinarian
The Texas .4&/1,,1 University Stystem
Laryngotracheitis (IT) is not an estalllislwd disf'a,,(' in T('x<I:-.
This gives Texas poultry produCf'rs a prodUl'Iion co,,! advLlntagt·
not enjoyed in states where the disease is univf'rsall: present. II'
LT were to hecome firmlv estahlished in T('xas, this advantagt'
would be lost. The t'xlwnse of vaccirlt's alolw would add more
than $1,000,000 annually to hroiler llwat ancl egg produl'lion
costs. Other direct and indirt'cl costs of "living" with the dist'ase
would be even greatt'r.
Laryngotracheitis is a respiratory diseas(' of chick('n.., ('au"ed
by a herpt'svirus and characterized by a numht'r of signs.
including coughing. gasping, walPry evt's, swollt'n sinust's. nasal
dischargt' and t'xpectoration of hlood\ l'xudate. Thl' virus pnkr"
the respiratory system or o('ldar are;\. r('plicating in the cells
which line tht' larvnx and trachea and causing ('(·11" in thi" art'a to
die. -\s tht' lining is sloughed. tilt' ullllerh'ing blood \,(,:-:-t,l" art'
t'xposed, cau:,>ing difficult breathing and ..,uff()l'ation. TIll' t\ pil'al
sign is gasping for air. The ehi('ken nlllsl "tretch its neck forward
and upward with t'ach inspiration. Blood i" ('ouglwd out.
splaltt'ring walls and floors. But many prt'st'nt-da\ outhreak:- art'
of a mild nat urt', re"t'mbling a mild \I'W('<ht It' di"east' or
inft'ctious hronchiti". Disease los"t's in afft·(·tt'd flock:-, may 1)(>
severf> as a result of lowert'd production (both t'gg and nwat),
elevated condemnation rate:,> (when broiler:-. are pro(·t'sst'd) and
mortality (up to SO pt'rcent in st'\'pre olltbrt>aks).
(hickens are primarily afft>(·tpd, Illlt in rare instanees IT ha'"
ht'f'n found in pheasants. rwafowis and turkt>:·s. Tlw vim.., ha"
never been recovered from otlll-'r avian spe('if's and t'ffort.., to
introduce tilt' virus into laboratorv marllmals. "'lll'h a" rahhit-. and
rodenls, havt' bet'n unsl)('ressful.
The disease usuallv pnters an area with the introduetion of
carrier hiI'd" or bv tilt' movement of man and contaminated
equipment. Once i~troduced to a su",ct'ptihll' flock, the LT \iru:-.
spreads rapidly by contact. Bird.., whirh rpcover from tht· di"'l'a"'I'
rna:' continut' to shed tilt' virus for prolongl'd Iwriods of time.
The incubation period of IT i" usuallv 0 to I;') c!<l\S, but the
dis('ast' has been found as soon a" 2 days following natural
exposure.
In endemic areas a special program of ~lIrv('i1lal\('f> ..,!lollid II('
activated. using strict rult'" and rt'glliation~ regarding proper
varcination of all chickens.
Laryngotrarhpitis modified tissue ('ldturt' VaCl'illt' mav he u~f'd
in Texas without rest rirtion. Chil'k Emhn 0 Origin (CEO)
varcine may be used upon tentative or confirmed diaplo"is of IT
hy an approvpcj laboratorY' and upon written agreement hptween
tl1l' Tt'xas Animal Health Commission and £lork owners.
c\.1·(·ording to tlH' manufacturer, the modified live virus chirken
tio.suI' culture origin vacrine does not offer the same degree of
pro!t'ct ion usually obtained from more virulent produrts. But
with it there' is no dangt'r of st'eding down the premises with LT
yiru~ which can spre·ad and cause tilt' disease.
\\.'hl'n a CEO vaccinatecl flock is moved, during the shedcling
period, nl'xt to an older f10rk that was Ilf'Ver vaccinated, the
\,iru.., start.., spreading through the older birds. It gradually
incre'ases in virulenre and pventuallv may cause an LT outbreak.
If a CEO VaCCillt' is uSI,d it should hp administered to all flocks on
a farm.
Containment and eradication of LT involve many factors,
including the judicious use of vaccines, quarantine and 'depopula.
tion by attrition.
The following control program should be initiated following an
ollthrf'ak:
Produrprs
• \\'I1I'n birds are to hI' introduced to the premises, determine
their SOUf<'I' and tht' vaccination program used with them.
"ew or sanitized crates should he used for shipment. Birds
vaccinated with CEO vaccine ran herome inferted with LT
and shed the virus without showing marked signs of the
diseast', A tight serurity program should hI' initiatpd on all
varcinatl'd flocks. CEO vaccinated birds should not enter a
clean (non-quarantillPd) area.
• Keep disinfectants available and use as indicated. The virus is
readil~' destroyed hy man~ disinfectants and is not highl~'
resistant outsicle the host. A solution of ,1 percent Cresol or 1
percent lye will inactivatt' LT virus in less than a minute.
\lost produch from reputable companips will perform sat is-
fal'tmih' if properh' applied.
• Provide an outside rereptacle for feed slips. Driw'rs should
not l'ntpr housl'o..
• Do not l'nt!:'r poultry hou:;es on other farms regardl!:'ss of
health status. Keep all visitors away from poultry houses.
Install "no admittanct''' signs.
• Lock all pOllltr~ hOllses and arrangt' an insidt' latch so that a
vio.itor cannot follow YOII into the house wht'n yOU are. .
working.
• \)(',Id hird~ should be rt'movl"d from tilt' houst' only in plastic
bags and buried or incineratt'd. Pits should be covered so that
rodents Of othpr predators cannot sprt'ad thl' diseast'. The
rL~I'ase can ht' spread hv impropt'r dead hiI'd disposal and
failurt' to praclirl' ~anitation procpdllrl'~.
• Grow!"rs and servicemen should not own hackvard Oocb-.
Evidence gathered in Ppnnsylvania indicatps that hachard
chicken flocks may Ill' carril'r" and constitute a rpsI'rvoir of
thl' disl'ase. {'sually only a "mall!H'lTentagl' of tilt' hiI'd" in tIlt'
flock rf'main carril'rs. hut tlIPS(' "I'rve to lH'rl'l'Iuate tl1l'
disl'a,,1' on the prl'mises and may spread it upon contact with
susct'ptiblp chickens. Carri"r hini" lila: (,Iilllinate the viru..., for
24 months.
• Do not leave straY ehickf'ns (not eVI'n one) in till' hOlhl' when
a f10ek is moved. -\lI-in. all-ollt pradic'es should hI' follow('d
on a premises basis.
• When birds are moved out of a house when' thprf' has been an
LT outbrf'ak, keep the house closed with the c'urtains over the
sides for at least 2 weeks. Tlw virus is normally destruwd at
99 degrees f. The lower the temperature, the lo'nger th~ virus
will survive outside the chickens.
• Do not remove littpr for at least two broiler growout"
following an outbreak or vaccination with CEO vacc'irH'. Littpr
from breeder Iwns ano commt'rcial lavers should 1)(' rellloveo
following tilt' movt'lIlt'nt of hirds. Litter from inff'cted Oocks
shollid be composkd ulHil'r pla"tic' Iwfort> ...,pn·ading on fil·lds.
• 'When LT is suspected. the grower should plact' four fresh,
dead birds in a heavy plastic bag for transportation to the
diagnostic laboratory. Live, sick birds should be transported
in a disposable crate. SUSpN·t Oocks "hould bl' treated as
positive until a diagnosis is made. Servicemen handling
infected birds should chang!" clothes and disinfect vehicles.
Visitors
{'nless ab"olutelv necessary. visitor" should not be allowed on
an infected premises. "aceination crews, servicemen and live-
haul news should conform to the following procedures:
• Park vehicles away from poultrv hOlls('S llt'ar the clt·an-llp
area.
• \"ear disinfected boots, clean overall" and di"po"ahll' caps.
• Prior to leaving the farm, place coveralls and other wa"hahll'
items in plastic bags to be laundered. Articles that cannot be
disinfected should be left on the farm.
• Shower, wash hair, clean fingernails, etr. before entering
another farm.
Feed Delivery
• Delivery men should staY out of how.;es.
• (ll'an clothes should be worn daih'.
• Ff't'd tickf'ts should bf' left in a mf'ssage box.
• Ft'ed should flf' delivered to infected premises last. During
inff'ction, deliverif's should be kept to a minimum.
• -\fler entf'ring an infpclt'd arpa, trucks should be c1paned.
Ef{l{ Pro('p.....wrs
• Producers should clpan and sanitize floors of egg and work
rooms.
• Clean and disinfect footwear dailv.
• Sanitize plastic f'gg flats, racks and other l"quipment before
It'aving or returning to the farm. Fiber egg flats should bf'
dp..;t rnvf'd,
• D{,liverv men should not go beyund the egg room. Wl"ar cll"an
o\'t'ralls whill" on tht, farm and Ipavl" tlll"m at the farm.
• <:It'an and disinfect the insidt> and outsidp of vl"hicles that
have enterpd an infpt'!ed arf'a,
Cal('hing Crpw
• <:lean. freshlv laundprpd clothes shoulrl be worn daily (and
changed het wepn farms).
• Buuts should fw rli~inft'l'led hefort' and aftf'r working in a
poultry house. Sneakprs should be laundered bl"fore entf'ring
a farm,
• Di..;pusable lunch hags shoulrl bl" used and Il"ft on tlw farm.
• Crt'\\' nlt'tlll){-'r~ mu"t not own or visit backyard poultry.
• Clean and disinff'ct all catching efjuirmpnt (hooks. nets,
fpnl'e-;. 1'1(',) before leaving a farm.
• (:It'all and di"infprt thl" intl"rior and l"xterior of thl" vehiclf'
used to haul the catrhing crew.
• Crt''''' should sho\\'f'r. wash hair and launder clothing whf'n
arri "ing IlOllW .
."lummary
• ProdlJ('pr,., IlI1lS1 eunform to strict sanitation and management
procedurf's 10 prt'vf'nt tilt' inlroduetion or movement of the
1.1' \'irus to npw local iOlls. Emphasis must be placf'd on
i-;olation. Disea-;p control is expensive hut its alternatives can
Iw disastrous,
• Programs to control flif's. rodl"nts. wild birds. backyard
poultr~,. and rets should be ongoing. Backvard, game and
specialty fowl art' located throughout thl" country; arl"
continually exchanged, traded and shown; and often are not
vaccinated.
• Houses that contained LT positive norks should be thoroughly
sprayed with a disinfectant.
• Laryngotracheitis virus can survive for long timp periocls
outside the chickf'n, clepending upon moisturf' ancl tf'm-
perature.
• Recovered or carrier nocks may rontinue to shed the virus for
prolonged periods of time. The house must he consiclered
contaminated.
• CEO vaccinated hircls ran hecome infcctf'd with IT and shed
the virus without showing marked signs of til(' disf'ase.
Vaccinated norks shoulcl he ('onsiderpd inff'cted.
• Vaccination can prevent losses. When possihle and practical,
modified tissue rulturf' vacrine should he uSt'cl.
• Not all outbrf'aks of IT art' of thf' sanw st'vcrity. Parental
immunitv, age, vaccination historv and till' virulf'nre of thf'
particular LT virus ran innuenre the severity of diseasf'
observed.
• Chick deliveries should he madt' to ('ontaminall·d farms on tlw
last trip of the day. The chirk hus should be properly
derontaminatpd hefore reuse.
• Egg nats from inff'cted or CEO varcinatecl prf'mises arC' to bf'
returnf'd to infectecl housf's; di!-'po!-'f'cl of; or disinfertf'd and
returned onlv to the farm from which tlwv (·arne.
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English

Infectious Laryngotracheitis.

https://oaktrust.library.tamu.edu/bitstream/1969.1/160194/7/Bull1608a.pdf

Infectious Laryngotracheitis.

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