Outbreaks of contagious ecthyma in camels {Camelus

Outbreaks of contagious ecthyma in camels {Camelus

Rev. sci. tech. Off. int. Epiz., 1994,13 (3), 939-945
Outbreaks of contagious ecthyma in camels
{Camelus dromedarius) in the Turkana
district of Kenya
C.G. GITAO *
Summary: Mortality among camel calves (Camelus d r o m e d a r i u s ) is one of the
most serious problems faced by camel herdsmen and, although there are several
reasons for this mortality, diseases play a major role. In an investigation
of
outbreaks of contagious ecthyma in camels in the Turkana district of Kenya,
four outbreaks were detected involving only camel calves. The principal
lesions
were distinct or largely coalesced pustules on the mouth, nose and
muzzle.
Direct electron microscopy of infected scabs was used to confirm the presence
of the virus. Secondary infection of the pustules was common in affected calves.
Morbidity
in affected herds was 100%, with no adult involvement.
Affected
calves were unable to suckle properly. In all outbreaks, there was a concurrent
outbreak of contagious pustular dermatitis in goat kids in the same
household.
Contagious
ecthyma is an important disease in camels, contributing
to calf
debility and eventually to high calf mortality.
K E Y W O R D S : Camels - Contagious ecthyma - Kenya - Outbreaks
Turkana.
-
INTRODUCTION
C o n t a g i o u s e c t h y m a i n c a m e l s (Camelus
dromedarius)
is a p a r a p o x v i r u s d i s e a s e
w h i c h h a s b e e n d e s c r i b e d in M o n g o l i a ( 4 , 2 ) , S o m a l i a (3), t h e f o r m e r S o v i e t U n i o n (11)
a n d t h e S u d a n (1). O n l y o n e o u t b r e a k h a s b e e n r e p o r t e d in K e n y a (7). N o i n v e s t i g a t i o n
h a s b e e n m a d e in a specific c a m e l - r e a r i n g a r e a t o d e t e r m i n e t h e g e o g r a p h i c a l s p r e a d of
t h e d i s e a s e . A s calf m o r t a l i t y is t h e m o s t i m p o r t a n t h e a l t h p r o b l e m f a c e d b y c a m e l
h e r d e r s ( 8 ) , s o m e t i m e s r e a c h i n g 5 0 % , it is i m p o r t a n t t o e x a m i n e a n y p o t e n t i a l f a c t o r
w h i c h m a y c o n t r i b u t e t o t h e debility of c a m e l calves a n d h e n c e t o s u c h m o r t a l i t y . Visits
w e r e t h e r e f o r e m a d e t o t h e T u r k a n a d i s t r i c t i n K e n y a , o n e of t h e p r i n c i p a l c a m e l r e a r i n g a r e a s in t h e c o u n t r y , a n d s k i n c o n d i t i o n s w e r e e x a m i n e d in s e v e r a l h e r d s .
* University of Nairobi, Department of Veterinary Pathology and Microbiology, P.O. Box 29053,
Nairobi, Kenya.
940
MATERIALS AND METHODS
Epidemiology
T h e T u r k a n a district is a n a r i d a r e a r e c e i v i n g less t h a n 500 m m of s c a t t e r e d rainfall
a n n u a l l y . I n t h i s d i s t r i c t , a p p r o x i m a t e l y 1 0 0 , 0 0 0 c a m e l s a r e r e a r e d b y p a s t o r a l i s t s in
h e r d s r a n g i n g in size f r o m 2 a n i m a l s t o 60 o r m o r e . T h e d i s t r i c t w a s v i s i t e d in t h e d r y
m o n t h of S e p t e m b e r , a n d 6 0 0 c a m e l s w e r e e x a m i n e d i n 30 h e r d s r a n g i n g i n size f r o m
2-60 animals. Skin conditions w e r e closely scrutinised a n d scabs w e r e o b t a i n e d from
suspected pox lesions.
E l e c t r o n microscopy
S k i n s c a b s f r o m i n f e c t e d c a m e l s w e r e g r o u n d a n d r e - s u s p e n d e d in a m i n i m u m
v o l u m e of p h o s p h a t e b u f f e r e d s a l i n e ( p H 7.2). A n e l e c t r o n m i c r o s c o p e grid w a s floated
o n a d r o p of v i r u s s u s p e n s i o n for t w o m i n u t e s , t h e n r e m o v e d a n d b l o t t e d w i t h t h e e d g e
of a p i e c e of b l o t t i n g p a p e r , a n d p l a c e d o n a d r o p of 2 % s o d i u m p h o s p h o t u n g s t a t e
( p H 6.6). A f t e r 90 s, t h e g r i d w a s b l o t t e d , air d r i e d a n d e x a m i n e d u s i n g a t r a n s m i s s i o n
e l e c t r o n m i c r o s c o p e o p e r a t i n g a t 60,000 V.
RESULTS
C o n t a g i o u s e c t h y m a w a s d e t e c t e d in c a m e l s in f o u r a r e a s of t h e T u r k a n a d i s t r i c t
( T a b l e I ) . O f 6 0 0 c a m e l s e x a m i n e d , c l i n i c a l c o n t a g i o u s e c t h y m a w a s d e t e c t e d in
67 a n i m a l s , i n d i c a t i n g a p o i n t p r e v a l e n c e r a t e of 1 1 . 2 % . I n t h e f o u r a r e a s , c o n t a g i o u s
e c t h y m a w a s f o u n d t o b e at t h e s a m e clinical stage, a l t h o u g h t h e a r e a s a r e v e r y far a p a r t .
T h e c o n d i t i o n h a d b e e n p r e s e n t for o n e w e e k a n d o n l y e i g h t - m o n t h - o l d c a m e l s w e r e
affected. M o r b i d i t y w a s 1 0 0 % in e a c h of t h e affected flocks.
T h e p r i n c i p a l clinical f e a t u r e o b s e r v e d w a s t h e a p p e a r a n c e of p u s t u l e s o n t h e n o s e ,
m u z z l e a n d lips (Fig. 1). M a n y of t h e cervical a n d m a n d i b u l a r l y m p h n o d e s w e r e s w o l l e n
a n d o e d e m a t o u s . Frequently, these swollen lymph nodes h a d b e e n b r a n d e d with a hot
i r o n , w h i c h is a c o m m o n p r a c t i c e a m o n g p a s t o r a l i s t s in t h e a r e a . P a r a p o x i n f e c t i o n w a s
c o n f i r m e d b y e l e c t r o n m i c r o s c o p y in m o s t c a s e s (Fig. 2 ) . T h e m a j o r i t y of t h e s e l e s i o n s
TABLE I
Outbreaks
of contagious
ecthyma
in the Turkana district
in camels and
of Kenya
goats
Camels
Location
Kakuma
Kalokol
Lokori
Lokitaung
No.
affected
Age
(months)
12
20
30
5
8
8
8
8
EM+: infection detected by electron microscopy
Goats
EM+
No.
affected
EM+
10
18
27
5
20
5
10
20
18
5
7
16
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Fiel
Pustules o n t h e m u z z l e and lips of a c a m e l calf infected with contagious e c t h y m a
h a d secondary infections a n d thick yellowish pus h a d accumulated b e n e a t h t h e scabs. In
a r e a s of t h e s k i n w i t h n o s e c o n d a r y i n f e c t i o n s , r a w h y p e r a e m i a w a s o b s e r v e d b e n e a t h
t h e s c a b . N o l e s i o n s w e r e o b s e r v e d o n t h e u d d e r s of t h e d a m s of t h e s e calves, n o r o n t h e
skin of a n y of t h e a d u l t c a m e l s e x a m i n e d .
I n all t h e a r e a s w h e r e o u t b r e a k s of c o n t a g i o u s e c t h y m a w e r e o b s e r v e d in c a m e l s ,
i n f e c t i o n w a s also a p p a r e n t in g o a t k i d s ( T a b l e I ) . L e s i o n s in k i d s w e r e of a similar t y p e
a n d at a similar s t a g e , s h o w i n g p u s t u l e s p r i n c i p a l l y on t h e lips, m u z z l e a n d n o s e .
E x t e n s i v e s e c o n d a r y i n f e c t i o n w a s also o b s e r v e d in g o a t k i d s , w i t h t h i c k y e l l o w i s h p u s
u n d e r n e a t h s o m e of t h e s c a b s (Fig. 3 ) . P o x l e s i o n s w e r e also visible o n t h e u d d e r s of t e n
d a m s s u c k l i n g s o m e of t h e affected g o a t k i d s .
DISCUSSION
C a m e l r e a r i n g is a difficult p r o c e s s , d u e t o t h e l o w r e p r o d u c t i v e r a t e of t h e c a m e l a n d
h i g h calf m o r t a l i t y ( s o m e t i m e s r e a c h i n g 5 0 % ) (8). It is t h e r e f o r e i m p o r t a n t t o e x a m i n e
s o m e of t h e f a c t o r s w h i c h m a y c o n t r i b u t e t o t h e w e a k e n i n g of c a l v e s a n d t h u s t o h i g h
mortality.
T h e c u r r e n t s t u d y i n d i c a t e s t h a t c o n t a g i o u s e c t h y m a is e n z o o t i c in c a m e l s in t h e
T u r k a n a d i s t r i c t of K e n y a , a n d is p r e s e n t p r i n c i p a l l y in c a m e l c a l v e s . T h e fact t h a t a
s i m i l a r c l i n i c a l s t a g e of t h e d i s e a s e w a s o b s e r v e d i n d i f f e r e n t g e o g r a p h i c a l a r e a s is
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FIG.
2
N e g a t i v e l y - s t a i n e d electron micrograph of contagious e c t h y m a virus (60,000x)
p r o b a b l y r e l a t e d t o t h e fact t h a t c a m e l s a r e s e a s o n a l b r e e d e r s a n d m a n y calves a r e
t h e r e f o r e b o r n at a p p r o x i m a t e l y t h e s a m e t i m e .
M o r b i d i t y of 1 0 0 % in c a l v e s h a s a l s o b e e n d e s c r i b e d b y o t h e r r e s e a r c h e r s , b u t this
r a t e w a s r e p o r t e d t o b e l o w ( 1 0 - 2 0 % ) in a d u l t c a m e l s ( 7 ) . T h e c o m m o n p r a c t i c e of
k e e p i n g all c a m e l calves in t h e s a m e s h e l t e r at n i g h t c o u l d b e r e s p o n s i b l e for t h e s p r e a d
of v i r u s b y c o n t a c t . T h e a b s e n c e of c o n t a g i o u s e c t h y m a in m a t u r e a n i m a l s is p r o b a b l y
d u e t o a n i m m u n e r e s p o n s e w h i c h is a b s e n t in v e r y y o u n g c a m e l s ; s u c h a p a t t e r n h a s
b e e n d e s c r i b e d for g o a t k i d s (10). I n this study, o n l y localised lesions o n t h e m u z z l e a n d
lips w e r e f o u n d . S i m i l a r s i g n s h a v e b e e n r e p o r t e d in S o m a l i a (6) a n d t h e S u d a n ( 1 ) .
G e n e r a l i s e d lesions i n v o l v i n g t h e distal p a r t s of t h e legs, t h e i n n e r t h i g h s a n d t h e v a g i n a
in f e m a l e s h a v e also b e e n r e p o r t e d (7).
A l l o u t b r e a k s o c c u r r e d in h e r d s w h e r e p a r a p o x v i r u s i n f e c t i o n w a s also o b s e r v e d in
g o a t k i d s r a i s e d n e a r b y . O t h e r r e p o r t s h a v e i n d i c a t e d t h a t o u t b r e a k s of c o n t a g i o u s
e c t h y m a in c a m e l s h a v e o c c u r r e d in a r e a s w h e r e orf is p r e s e n t in s h e e p (7). O u t b r e a k s
of p a r a p o x v i r u s i n f e c t i o n in a l p a c a s (Lama pacos), s t e e n b o k (Raphicerus
campestris)
(9) a n d m a n y o t h e r a n i m a l s a r e t h o u g h t t o b e of o v i n e o r c a p r i n e o r i g i n ( 1 0 ) . T h i s is
p r o b a b l y also t h e c a s e for c o n t a g i o u s e c t h y m a in c a m e l s .
N o p r o g r a m m e e x i s t s f o r t h e v a c c i n a t i o n of c a m e l s o r g o a t s a g a i n s t c o n t a g i o u s
e c t h y m a virus in t h e c a m e l - r e a r i n g a r e a s of K e n y a , p r o b a b l y d u e t o lack of i n f o r m a t i o n ,
t h e v a s t d i s t a n c e s t o b e c o v e r e d in t h e a r i d l a n d s a n d t h e l a c k of r e s o u r c e s . T h i s s t u d y
m a y t h e r e f o r e s e r v e as a basis for t h e e s t a b l i s h m e n t of s u c h a p r o g r a m m e .
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FIG.
3
Pustules o n t h e m u z z l e and lips o f a goat kid infected with contagious e c t h y m a
O t h e r c o n d i t i o n s w h i c h m a y b e similar t o c o n t a g i o u s e c t h y m a w e r e p r e c l u d e d b y t h e
clinical signs. M a n g e i n f e c t i o n is a s s o c i a t e d w i t h g e n e r a l p r u r i t i s a n d a l o p e c i a o n m a n y
p a r t s of t h e b o d y s u r f a c e . C a m e l s a r e n o t likely t o suffer clinically f r o m f o o t a n d m o u t h
disease, although the animals m a y react to experimentally-inoculated foot and m o u t h
d i s e a s e v i r u s (5).
*
* *
ÉPIDÉMIES D'ECTHYMA
(CAMELUS
DROMEDARIUS)
C.G. Gitao.
CONTAGIEUX
CHEZ LES
DROMADAIRES
D A N S LE DISTRICT D E T U R K A N A A U KENYA. -
Résumé : La mortalité des jeunes dromadaires ( C a m e l u s d r o m e d a r i u s ) est l'un
des problèmes les plus graves auxquels soient confrontés les éleveurs. Parmi les
différentes causes de cette mortalité, les maladies jouent un rôle majeur. Lors
d'une étude sur l'ecthyma contagieux chez les dromadaires,
effectuée dans le
district de Turkana, au Kenya, quatre foyers ont été décelés qui ne concernaient
que de jeunes animaux. Les principales
lésions consistaient
en des pustules
isolées ou largement confluantes, localisées dans la bouche, dans les naseaux et
sur le museau. L'observation
directe au microscope électronique
des croûtes
infectées a permis de confirmer la présence du virus. Une infection
secondaire
des pustules a été fréquemment
observée chez les jeunes dromadaires
atteints.
944
La morbidité était de 100 % dans les élevages atteints, mais elle ne concernait
pas les adultes. Les chamelons étaient incapables de téter correctement.
Dans
tous les cas, on a observé une épidémie concomitante
de dermatite
pustuleuse
contagieuse
chez les chevreaux
dans la même exploitation.
L'ecthyma
contagieux est une maladie grave du dromadaire chez lequel elle entraîne une
asthénie, voire une mortalité élevée dans le cas des jeunes sujets.
M O T S - C L É S : Dromadaires - Ecthyma contagieux - Foyers - Kenya Turkana.
*
* *
B R O T E S D E E C T I M A C O N T A G I O S O E N LOS D R O M E D A R I O S
(CAMELUS
DROMEDARIUS)
D E L D I S T R I T O D E T U R K A N A , E N K E N I A . - C.G. Gitao.
Resumen: La mortalidad de los dromedarios jóvenes ( C a m e l u s d r o m e d a r i u s )
es uno de los problemas más graves que deben enfrentar los ganaderos;
entre
sus causas, las enfermedades
ocupan un lugar principal.
En ocasión de un
estudio sobre el ectima contagioso en los dromedarios en el distrito de Turkana,
en Kenia, se detectaron cuatro brotes que incluían solamente animales
jóvenes.
Las lesiones más importantes
consistían en pústulas aisladas o
ampliamente
confluentes,
localizadas
en la boca, las narices y el hocico. La
observación
directa en microscopio electrónico de las costras infectadas permitió
confirmar
la presencia del virus. Una infección secundaria de las pústulas se observó a
menudo en los jóvenes dromedarios afectados. La morbilidad fue del 100% en
los rebaños afectados, pero no implicaba a los animales adultos. Los más
jóvenes eran incapaces de mamar correctamente.
En todos los casos, se
observaron
brotes concomitantes
de dermatitis pustulosa contagiosa en los
cabritos de la misma explotación.
El ectima contagioso
es una
enfermedad
grave del dromedario,
que puede causar astenia e incluso una
mortalidad
elevada en los animales
jóvenes.
P A L A B R A S C L A V E : B r o t e s - D r o m e d a r i o s - E c t i m a contagioso - K e n i a Turkana.
*
*
*
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