Parasit. Hung.
6- 1973.
Population Density of Small Vertebrates and their Role as Hosts of Ticks NOSEK, J. — CERNY,
V. — G U L Y Á S , M . -
MOLNÁR, E . —
E R N E K , E . — K O Z U C H , O. — L A B U D A , M. Institute of Virology S A S , Bratislava — National Institute o f Public Health, Budapest
"Population Density o f Small V e r t e b r a t e s and t h e i r Role as Hosts o f T i c k s " - Hosek, J . , Cerny, V-, Gulyás, M., Molnár, E., Ernek, E., Kozuch, 0 . , Labuda, M. - P a r a s i t . Hung. 6 . 239-246. 1973. I n C e n t r a l European TBE f o c i s m a l l mammals, such as bank v o l e , y e l l o w necked mouse and l o n g - t a i l e d fieldmouse»are t h e main h o s t s f o r Ixodes r i c i n u s l a r v a e . B i r d s are t h e main h o s t s o f nymphs i n n a t u r a l f o c i o f the t h e r i o d i c t y p e ; s m a l l r o d e n t s and i n s e c t i v o r e s may be the main h o s t s o f nymphs i n TBE f o c i o f the t h e r i o - b o s k e m a t i c t y p e . As a r u l e s m a l l i n s e c t i v o r e s c o n t r i b u t e less t o the l e v e l of p o p u l a t i o n densi t y o f t i c k s t h a n do s m a l l r o d e n t s . Por maintenance o f t h e v i r u s and the t i c k p o p u l a t i o n i n an e l e m e n t a r y f o c u s o f TBE o n l y those h o s t - p o p u l a t i o n s a r e o f i m p o r t a n c e which c o i n c i d e w i t h t h e seasonal and s p a t i a l i n c i d e n c e o f t i c k s . Very h i g h p o p u l a t i o n d e n s i t y o f nymphs and a d u l t t i c k s , over 600 spe cimens f o r 100 square m e t e r s , was observed i n g r a z i n g f o r e s t s and i n ecotone p a s t u r e - f o r e s t i n r e g i o n s w i t h game keeping.
I n t h e whole d i s t r i b u t i o n a r e a o f n a t u r a l f o c i of tick-borne e n c e p h a l i t i s (TBE) o f Western s u b t y p e , o f b a s i c i m p o r t a n c e as v e r y f r e q u e n t maintenance h o s t s ( r e s e r v o i r s ) of the v i r u s are s m a l l i n s e c t i v o r e s : common shrew Sorex a r a n e u s , European mole Talpa europaea and s m a l l r o d e n t s such as bank v o l e C l e t h r i o n o mys g l a r e o l u s , w h i c h a r e i n some p l a c e s a s s o c i a t e d w i t h y e l l o w necked mouse Apodemus f l a v i c o l l i s and l o n g - t a i l e d f i e l d m o u s e Apodemus s y l v a t i c u s . At the same t i m e t h e range o f h o s t s o f the I x o d e s r i c i n u s t i c k , w h i c h i s c o n s i d e r e d t o be t h e main
v e c t o r of TBE, was
found
t o extend
t o more t h a n 15 0 species o f
vertebrates. The mentioned s p e c i e s of mammalian öynusia are n o t o n l y impor t a n t as maintenance h o s t s but a l s o as v e r y f r e q u e n t and main h o s t s of l a r v a e o f I . r i c i n u s i n C e n t r a l European n a t u r a l f o c i of TBE. Prom t h i s p o i n t o f v i e w " C l e t h r i o n o m y s g l a r e o l u s , Apode mus f l a v i c o l l i s and A. s y l v a t i c u s a r e o f p r i m a r y s i g n i f i c a n c e . Small i n s e c t i v o r e s as a r u l e p l a y a minor r o l e as h o s t s o f I . r i c i n u s l a r v a e and a r e l e s s i m p o r t a n t t h a n s m a l l r o d e n t s ( P i g s . 1 and 2 ) . The p o p u l a t i o n " d e n s i t y o f r e p t i l e s , b i r d s and i n s e c t i v o r e s seems t o be much more constant t h a n t h a t o f s m a l l r o d e n t s d u r i n g t h e year and d u r i n g t h e s u c c e s s i v e y e a r s ; thus when o n l y a few s m a l l r o d e n t s a r e a v a i l a b l e , b i r d s t o g e t h e r w i t h i n s e c t i v o r e s become an i m p o r t a n t source o f b l o o d f o r I . r i c i n u s l a r v a e i n n a t u r a l f o c i of TBE o f t h e r i o d i c type . However, i n the y e a r s when t h e p o p u l a t i o n d e n s i t y o f s m a l l mammals i s n o r m a l , o n l y a s m a l l p e r c e n t a g e o f the l a r v a e f e e d s on b i r d s , most o f them p a r a s i t i z i n g the mammals.
P i g . 1 : Humber o f engorged l a r v a e o f I x o d e s r i c i n u s on s m a l l r o d e n t s and i n s e c t i v o r e s . C a l c u l a t i o n was made by t h e f o r m u l a of O l s u f j e v ( 1 9 5 3 ) : Humber o f engorged t i c k = D e n s i t y of ho3t per 1 h e c t a r e / I n d e x o f i n f e s t a t i o n l o n g e v i t y . 1 . ábra: Vért szívott Ixodes r i c i n u s lárvák száma k i s rágcsáló kon és rovarevő gazdákon. A számítás O l s u f j e v (1953) alábbi formulája alapján történt: Vérszívott k u l l a n c s o k száma = Gazdaállatok száma 1 hektár területen/A fertőzöttség tartamá nak i n d e x e . C o l l e c t i o n l o c a l i t i e s i n Hungary - Magyarországi gyűjtőhelyek: P = Pertőboz; G = G i c ; T = Tómalom; M = Mosonmagyaróvár; D = Debrecen. Time o f c o l l e c t i o n - A gyűjtés i d e j e : IV = A p r i l ; V = May; I X = September; X = O c t o b e r . Hosts - Gazdák: I = I n s e c t i v o r a ; R = R o d e n t i a ; Mm = Mus mus c u l u s ; Clg = C l e t h r i o n o m y s g l a r e o l u s ; A f = Apodemus f l a v i c o l lis; As = Apodemus s y l v a t i c u s ; Aa = Apodemus agrárius; Ma = Microtus a r v a l i s ; Ps = Pitymys s u b t e r r a n e u s ; Sm = Sorex minu tus; Ta = T a l p a europaea; Sa = Sorex araneus; CI = C r o c i d u r a l e u c o d o n ; Cs = C r o c i d u r a s u a v e o l e n s .
The degree of i n f e s t a t i o n and h o s t p r e f e r e n c e by t i c k s o f v e r t e b r a t e s i n an a r e a w i l l d e t e r m i n e t h e i r p o t e n t i a l importance in maintaining natural f o c i of i n f e c t i o n . The i m p o r t a n c e o f v e r t e b r a t e s as h o s t s t o t h e t i c k s w i l l depend on the average seasonal t o t a l number o f t i c k s per i n d i v i d u a l specimens f o r each s p e c i e s as w e l l as on s p e c i e s p o p u l a t i o n d e n s i t i e s . I n d i r e c t c o r r e l a t i o n e x i s t s between t h e p o p u l a t i o n d e n s i t y o f h o s t s and t i c k - l o a d . T h e t i c k - l o a d f o r i n d i v i d u a l s p e c i e s would appear to be r e l a t e d t o h o s t s i z e . F u r t h e r , t h e t i c k - l o a d on v e r t e b r a t e h o s t s may be r e l a t e d to their home r a n g e . We have ob served t h a t more i s o l a t e d w i d e - r a n g i n g y e l l o w necked mouse and l o n g - t a i l e d f i e l d m o u s e a c q u i r e s much more t i c k s than hosts w h i c h move ( F i g . l ) . The h i g h e r i n f e s t a t i o n of male mice i s a l so a t t r i b u t a b l e t o t h e i r g r e a t e r m o b i l i t y . For maintenance o f v i r u s and t i c k p o p u l a t i o n i n a n a t u r a l f o c u s o n l y those p o p u l a t i o n s of h o s t a r e of i m p o r t a n c e , w h i c h c o i n c i d e w i t h t h e seasonal and s p a t i a l i n c i d e n c e o f t i c k s . I t i s necess ary t o add t h a t t h e s i g n i f i c a n c e o f a g i v e n s p e c i e s as t i c k host i n d i f f e r e n t h a b i t a t s may be q u i t e d i f f e r e n t . S p a t i a l co i n c i d e n c e o f t i c k and host ( e c o l o g i c a l n i c h e ) comes here i n t o c o n s i d e r a t i o n , e. g., the European mole i n f o r e s t s of C e n t r a l Europe may be h e a v i l y i n f e s t e d w i t h l a r v a e and nymphs of I . r i -
Fig. 2.
2: R e l a t i v e i n c i d e n c e o f l a r v a e , nymphs and female of I x o d e s r i c i n u s on v a r i o u s h o s t s p e c i e s .
imagoes
ábra: Ixodes r i c i n u s lárvák, nymphák és nőstény imágók v i szonylagos előfordulása különféle g a z d a f a j o k o n . L = l a r v a e - lárvák; N = nypmhs - nymphák.
• [~J = Small r o d e n t s and i n s e c t i v o r e s - Kisrágcsálók és rovarevők 0 - B i r d s - Madarak [*~\ - B i g g e r r o d e n t s and i n s e c t i v o r e s - Nagytermetű rágcsálók és rovarevők ^ j j = Free l i v i n g u n g u l a t e s - Vadon élő patások |~*~| = C a r n i v o r a - Ragadozók • = R e p t i l i a - Hüllők P] = Grazing g o a t s - Legelőn t a r t o t t kecskék
cinus, while
i n meadows t h i s s p e c i e s i s
example i s g i v e n f r o m p a s t u r e s
non-infested.
of Scotland^ where the
Another
population
d e n s i t y o f t i c k s i s v e r y h i g h but
the mole i s v e r y s c a r c e l y i n
f e s t e d because i t l i v e s
l a y e r of
I960).
The
i n deep
l i m i t e d home range
common shrew, i s one of i n f e c t i o n
of small
humus s o i l
(VARMA,
mammals, such
as
the
o f the f a c t o r s i n m a i n t a i n i n g n a t u r a l f o c i
(NOSEK e t a l . , 1 9 7 2 ) . C o n v e r s e l y , on the b a s i s
marked a n i m a l s and
their virological
and
serological
of
examin
a t i o n i t i s p o s s i b l e t o f i n d so c a l l e d " m i c r o f o c i " . B i r d s , as h o s t s o f the t i c k s or the v i r u s , may be capable o f e s t a b l i s h i n g new f o c i o f i n f e c t i o n i n areas i n the same l a n d scape o u t s i d e the home range o f a p a r t i c u l a r population of s m a l l mammals. B i r d s may a l s o be able t o i n t r o d u c e t i c k s i n t o areas f r o m which t i c k s have been e r a d i c a t e d or t h e i r number g r e a t l y r e d u c e d . The p o p u l a t i o n d e n s i t y o f t i c k s i n an over f l o w e d Danube r e g i o n r e g a i n e d i t s n o r m a l v a l u e i n a 4 y e a r pe riod . The p o p u l a t i o n d e n s i t y per 1 h e c t a r e o f s m a l l mammals i n the TBE f o c u s T o p o l ' c i a n k y ( T r i b e c M o u n t a i n ) , a s s e s s e d by means o f the m a r k - r e l e a s e - r e c a p t u r e m e t h o d h a s been e s t i m a t e d : 7
1966
1967
1968
45 75
50 90
20 42
Spring Autumn The
average p o p u l a t i o n d e n s i t y f o r
by means o f carbon d i o x i d e 46,000 nymphs and i t was
ing i n i n d i r e c t hosts
The
50,000 a d u l t s ,
760,000 l a r v a e ,
1 hectare
technique
in
ticks,assessed
w h i l e a t the b e g i n n i n g
16,000 nymphs and
correlation
of
m i d - A p r i l 1969, was
with
the
3,300 a d u l t s
of
of
May
only be 7
population density
of
(MOSEK and KOZUCH, 1 9 7 0 ) .
protection
and
preservation
of h u n t i n g games, such as
red
deer, roe d e e r , f a l l o w deer, w i l d b o a r s , w h i c h are u s u a l l y hea v i l y parasitized
by I . r i c i n u s , f i r s t o f
a l l with adult
ticks,
as w e l l as t h e g r a z i n g o f f a r m animals c o n t r i b u t e s u b s t a n t i a l l y t o t h e i n c r e a s e o f t i c k p o p u l a t i o n . The optimum c o n d i t i o n f o r increasing population density of t i c k s e x i s t s i n grazing f o r e s t s o r i n ecotone p a s t u r e - f o r e s t i f p a r a l l e l l y a h i g h popu l a t i o n d e n s i t y o f small r o d e n t s o c c u r s . I n t h e area o f t i c k d i s t r i b u t i o n , n a t u r a l f o c i o f TBE w i l l be i n d i c a t e d by t h e presence o f v i r u l i f e r o u s t i c k s . A l o w i n f e c t i o n r a t e , though d i f f i c u l t t o d e t e c t , could s t i l l e f f e c t i v e l y m a i n t a i n v i r u s a c t i v i t y i n an e l e m e n t a r y f o c u s . A m p l i f y i n g f a c t o r s such as u n u s u a l l y l a r g e p o p u l a t i o n s o f s m a l l mammals due t o c y c l i c a l changes 7 c o u l d r e s u l t i n i n c r e a s e d p o p u l a t i o n s o? t i c k s and an i n c r e a s e d r a t e o f i n f e c t i o n . f
N O S E K , J . - C E R N Y , V . - G U L Y Á S , M. - M O L N Á R , E . - E R N E K , E . K O Z U C H , O . - L A B U D A , M. : K i s e m l ő s ö k populáció-sürusége és szerepük
a kullancsok közvetítésében
Az ún . k u l l a n c s - e n c e p h a l i t i s közép-európai természeti gócaiban a R o d e n t i a és az I n s e c t i v o r a rendbe tartozó kisemlősök, első sorban az e r d e i pocok, az e r d e i egér és a sárga nyakú e r d e i egér az Ixodes r i c i n u s lárvák l e g f o n t o s a b b gazdái. E kisemlősf a j o k nagy egyedszámban való előfordulása egybeesik a k u l l a n csok aktivitási idejével. A k i s e b b rovarevők kevésbé jelentős s z e r e p e t töltenek be a k u l l a n c s o k terjesztésében, m i n t a k i s rágcsálók. A k u l l a n c s o k elszaporodására a vadgazdálkodási körzetekben azo kon az erdőkön és feltételek,
bozótos legelőkön találhatók
amelyeken háziállatokat
l y e k e n a k u l l a n c s nymphák
és imágók száma
négyzetméterenkénti 600 példányt i s .
a legkedvezőbb
i s l e g e l t e t n e k . I l y e n he m e g h a l a d h a t j a a 100
References
NOSEK, J . - KOZUCH, 0 - : New a s p e c t s i n t h e e c o l o g y o f t i c k
vec
t o r s . - F o l i a Par. (Praha) 1 7 . 327-329. 1970. NOSEK, J . - KOZUCH, 0 . - CHMELA, J . : C o n t r i b u t i o n l e d g e o f home range i n common shrew
t o t h e know
Sorex araneus L —
- O e c o l o g i a ( B e r l i n ) 9_. 5 9 - 6 3 . 1 9 7 2 .
VARMA, M. G. R.: I 9 6 0 . P e r s o n a l
Received: 3 0 . 1 . 1973-
communication.
Dr. NOSEK, I . I n s t . V i r . SAS Bratislava Ulinska Dolina 9 Czechoslovakia
