b i (RVF virus, Bunyaviridae genus...
b
i
(RVF virus, Bunyaviridae genus Phlebovirus, is an arthropod-borne vira! disease
primarily affecting domestic animals, first isolated during an epizootic in 1930 in
Kenya.)
( in human, pathology was reported as an non-fatal febrile illness , but during the
!ast epizootics hemorrhagic fever syndroms and high fata!ity rate were observed.
Encepha!itis and chorioretinitis were atso observed. )
Egyp?: (80-700% of the ewes aborted, 860% of the adult animals died, and
mortaiity in the few lambs present approached 100%. )
(Severe clinical manifestations in human with high mortality rate were reported. )
( The question of endemicity of RVF virus in epizootics areas was unresolved and
needed definitive investigation.)
(in southern Mauritania with 15% positive domestic animal).
!gM anti bodies
detected in the sera of came! breeders indicated a recent circulation of ?he virus.
No correlation was observed in animais with reported abortion.
Saluzzo et al.
(1986) suggested that ample opportunity for epidemic-epizootic RVFV
?ransmiision existed in the Senegal River Basin of northern Senegal and
Sou?hern Mauritania.
1987 outbreak 385 cases reported (with 11% fatality rate) during an epizootic
among domestic ruminants. Strains of RVFV were iso!ated from people coming
:
from 225 kms (135 miles) east of Rosso and 6Qkms (35 miles) west of Rosso.
RVFV infected a high proportion of the domestic animais in the areas where
human disease reports were received. A much higher proportion of the animals
tested had RFV antibodies than tha? found among the human popuiation. This
once emphasizes the important role of domestic animals as amplifying hosts of
RVFV.
The ecological environment of the Senegal River Basin was recently
modified, in a large water conservation scheme, by the bulding of dams on the
Senegal river: in the Delta the Diama dam as a sait water barrier dam and in the
Upper curse in south-eastern Mali (Manantali dam). This possibly was an
additive factor in the occurence in the fal! of 1987. Developments in the areas
have encouraged migration and RVFV risk outbreak increased.
Results
Between the 1988- 1990 period , a significant decrease was giobaly observed
either by Elisa (24% in 1988 to 10,5% in 1990) or by neutralizaiion test
(X2= 29,76 ddl=2 p<O,OOl) was observed by Elisa and by NT (23 % in 1988,
19% in 1989 and 7% in 1990) (X2= 43,58 ddl=2 p<O,OOl )
A negative gradient from West to East was reported: by EL!SA: delta 46%,
middie basin 19% and Upper basin 25%
In the midd!e basin area, no significant variations of RVFV prevalence were
detected during the three year observation: 19 % in 1968 and 1989, 16% in 1990.
but by NT, significative variation X2= 7,88 ddl=2
We observed a similar pattern of antibody prevalence by neutralization test: a
high 1988 RVFV antibody preva!ence 77% in the lower basin, 19 % in the middle
basin and in the Upper basin:
( X2 = 70,7 ddl=2 p<O,OO!) between the 3
nreas). in the lower basin for the 3 years period the decrease is highly
significant. X2= 65,14 ddl=2 p ~0,001.
ovine-yoat : In 1990 non significant difference: X2= 0,56 ddl=l, with 6,6% positive
ovine and 7,2%caprine.
(in 1989, non significant difference: X2= 1,68 ddl=l )
juveniie , Young adults ( 2 to 6 adult teeth by jaw or moreless l to 3 ye;as-old) and
adults (8 teeth).
- in juveniles the percentage was significatively lower than in another age groups
(adults) In 1989 X2= 48,71 ddl=2 , in 1990 X2= 28,70 ddl = 2
The rapid renewal (turn-over) of small ruminant population, estimated in
sahe!ian conditions to about 50% animals one year old or less, is an important
factor for the RVFV prevalence decrease observed. In our samples, the Young age
group represented 33% of the total.
A national RVFV prevalence survey conducted in november 1987- february 1988
in several places as indicated in the map
northern area:St-Louis, Louga isohyete 300mm
central area: Thies, Fatick, Kaolack Diourbel isohyete 600mm
southern area: Tambacounda,Zigunchor, Kolda isohyete 900mm
T. The results prsented correlate with negative attempts of RVF virus isolations
from susceptible vectors collected in the delta area in the last 2 years, indication
of a viral low activity (1988-l 990).
SLIDE 1
TITLE AUTHORS
SL!DE 2
PREVALENCE iN SOUTHERN MAURITANIA 1985
SLIDE 3
MAP OF NORTH SENEGAL
SLIDE 4
1988-1990 SEROSURVEY RESULTS TABLE
SLIDE 5
GRAPHE ELISA REPARTITION BY AREAS
SLIDE 6
GRAPHE NEUTRALIZATION TEST REPARTITION BY AREAS
SCIDE 7
GRAPHE REPARTITION BY AGE GROUP AND SPECIES IN 89-90
SLIDE 8
GRAPHE COMPARISON OF PREVALENCE FROM 1982 TO 1990 LOWER BASIN
SLIDF 9
MAP OF SENEGAL; NATIONAL SEROSURVEY IN NOV :987-FE& 90
SLIDE 1
f’OST-EP!ZOOTIC PREVALENCE OF RIFT VALLEY FEVER ANTIBODY IN SMALL RUMINANTS
f:ROM THE SENEGAL RIVER BASIN (1988 -1990)
AUTHORS:
YAYA THIONGANE ISRA, H.G. ZELLER
PASTEUR INSTITUTE, H.G. FATY
AND J.A. AKAKPO, DAKAR UNfVERSITY VETERINARY SCHOOL, J.P. GONZALEZ, ORSTOM
THIS WORK IS PART OF A COLLABORATIVE STUDY BETWEEN THE SENEGALESE
!NSTITUTE FOR AGRICULTURE RESEARCH, THE PASTEUR INSTITUTE AND ORSTOM.
THE RIFT VALLEY FEVER IS AN ARTHROPOD-BORNE VIRAL DISEASE PRIMARLY
AFFECTING DOMESTIC ANIMALS AND SECONDARLY CAUSING SEVERE OUTBREAKS IN THE
HUMAN POPULATION OF AFRICA.
IT PRODUCES A ZOONOSIS AMONG RUMINANTS, CAUSING HEPATITIS WITH
YECROSIS, ABORTION IN ADULTS AND MORTALITY IN YOUNG OFFSPRING.
’
---IN EASTERN AFRICA, IN 1977 AND AGAIN, IN 1978, EXTENSIVE EPIZOOTICS OCCURRED IN
SEVERAL AREAS OF THE NILE DELTA AND VALLEY IN EGYPT.
--- AGA!N THE VIRUS WAS ISOLATED IN 1979 AND 1980 ALTHOUGH WIDESPREAD
EIPIZOOTICS DID NOT OCCUR IN THESE YEARS.
--IN WESTERN AFRICA, RVF VIRUS WAS ISOLATED FROM AEDES AEDlMORPHUS IN
BURKINA FASO IN 1983, FROM AEDES DALZIELI IN SOUTH-EAST PART OF SENEGAL IN
KEDOUGOU !N 1974 AN3 1983 AND FROM CUL!COIDES IN NIGERIA IN 1967.
SLIDE 2
IN 7985, A LARGE FOCUS OF RVF VIRUS CIRCULATION WAS IDENTIFIED IN THE SENEGAL
RIVET? AREA. (15% PREVALENCE AMONG DOMESTIC ANIMALS)
IGM ANTIBODIES DETECTED IN THE SERA OF CAMEL BREEDERS INDICATED A RECENT
CIRCULATION OF THE VIRUS.
DURING THE 1987 RAINY SEASON, EXTENSIVE EPIZOOTICS OF RVF VIRUS
OCCURED IN THE SENEGAL RIVER BASIN AMONG DOMESTIC RUMINANTS.
MOREOVER A TOTAL OF 385 HUMAN CASES WERE REPORTED IN MAURITANIA AT THE
ROSSO HOSPITAL .
AGAIN, IN OCTOBER 1988, AN ACTIVE CIRCULATION OF RVF VIRUS WAS OBSERVED IN
MAURITAN!A AND HERDS OF DOMESTIC ANIMALS SHOWED SIGNIFICANT PERCENTAGES OF
RVFV IGM.
THE OCCURENCE OF SUCH VIRAL MANIFESTATIONS PROMPTED US JO EVALUATE
THE DEGREE OF !MMUNITY AMONG SMALL RUMINANTS IN WHATAPPEARED TO BE A RISK
AREA
SL!DE 3
WE SJUDIED THE PREVALENCE OF RVFV ANTIBODIES !N SMALL RUMINANTS (SHEEP AND
GOATS) ALONG THE LEFT BANK OF THE SENEGAL RIVER BASIN.
THIIEE AHEAS WEHE DEFINED: ON THE MAP:
- UP?ER BASIN (MATAM), MIDDLE BASIN (PODOR) AND LOWER BASIN
(DAGANA).
SELECTED LOCATIONS WERE RANDOMLY CHOOSEN.
ANIMALS OF 2 OR MORE HERDS BY LOCATION WERE BLEEDED WITHOUT INDIVIDUAL
TAGGING.
SPEC!ES, SEX AND AGE (ADULT TEETH) OF THE ANIMALS WERE REPORTED, SO
ABORTIONS, HIGH MORTALIJY.. .
SERA WERE TESTED:
- PY FLISA (USING A HUMAN STRAIN FROM THE 1987 MAURITANIAN OUTBREAK) FOR IGG
AND IGM DETECTION
- AND BY NEUTRALIZATION TEST (USING THE VACCINE SMITHBURN STRAIN) IN TWO
DIFFERENT LABORATORIES AND RESULTS WERE COMBINED.
SLIDE 4
293 SERA FROM SHEEP AND GOA~S WERE COLLECTED IN AUGUST 1988,324 IN AUGUST
1989 AND 583 IN SEPTEMBER 1990
BETWEEN THE 1988- 1990 PERIOD , A SIGNIFICANT DECREASE WAS GLOÇIALY OBSERVED
EITHER BY ELISA (24% IN 1988 TO 10,5% IN 1990) OR BY NEUTRALIZATION TEST (23 % IN
1988 TO 7% IN 1990)
tN A MORE DETAILED ANALYSIS, WE OBSERVED A SIGNIFICATIVE DECREASE OF ANTIBODY
PR-VALENCE IN THE LOWER BASIN AND IN THE UPPER BASIN EITHER BY ELISAAND
NEUJRALIZATION TEST.
IN THE MIDDLE BASIN AREA, NO SIGNIF!CANT VARIATIONS OF RVFV PREVALENCE WERE
DETECTED DURING THE THREE YEAR OBSERVATION PERIOD BY ELISA :
19% IN 1988 AND 1989,16% IN 1990.
SLIDE 5
!N AUGUST 1988, AN HIGHER PREVALENCE WAS OBSERVED IN THE LOWER BASIN WHERE
THE ‘987 OUTBREAK OCCURED.
iN AUGUST 1989, A HIGHLY SIGNIFICANT DECREASE OF PREVALENCE IN THE LOWER BASIN
WAS OSSERVED : 45,7% IN 88, 25,6% IN 89, AND, AGAIN, IN 1990: 10,5%.
IN THE UPPER BASIN AREA THE DECREASE IS SIGNIFICANT IN THE PERIOD 1988-1990.
IN 1388, RVFV IGM WERE DETECTED IN 4 ANIMALS FROM THE THREE STUDIED AREAS.
IN 2 CASES, SERA WERE IGM POSITIVE, IGG NEGATIVE BY ELISA AND POSITIVE BY
NEUTRALIZATION TEST.
IN 1989, ONLY TWO IGM SERA WERE DETECTED (ONE FROM THE UPPER BASIN AND ONE
FROM THE MIDDLE BASIN).
AND IN 1990 AN ABSENCE OF RVFV IGM POSITIVE SERA
i)
SLIDE 6
A S’MILAR PATTEHN OF RVFV ANTIBODY PREVALENCE WAS OBTAINED BY
NEUTRALIZATION TEST :
THE 1968 HIGH PREVALENCE IN THE LOWER BASIN (77% VERSUS 46% BY ELISA)
A GLOBAL DECREASE OF ANTIBODY PREVALENCE ON THE 3 YEAR-PERIOD
AND A KITICEAELE DECREASE IN THE MIDDLE BASIN AREA (19% IN 1988,16% IN 1989 AND
11% IN 1990)
SLlDE 7
THE PREVALENCE OF RVF VIRUS ANTIBODY AMONG SMALL RUMINANTS SHOWED
NO S!C,Y!FICANT DIFFERENCES BETWEEN SHEEP AND GOATS.
HOWEVER, THERE WERE VARIATIONS OF PERCENTAGE OF POSITIVE ANIMALS BY AGE
GROUP:
JUVENILE, YOUNG ADULTS AND ADULTS.
IN JUVENILES THE PERCENTAGE WAS SIGNIFICATIVELY LOWER THAN IN ANOTHER AGE
GROUPS (ADULTS)
SLIDE 8
THE CC’>b!PARISON OF PRE- AND POST-EPIDEMIC RVF VIRUS IGG AND IGM ANTIBODY AS
SI-iOWN HERE AMONG r)OMESTIC ANIMALS IN THE LOWER BASIN OF THE SENEGAL RIVER
’
SMOWED:
- AN ABSENCE OF VIRAL ACVTIVITY IN 1982,
-A 3% PREVALENCE IN 1983 AND 85% PREVALENCE IN
NOVEMBER 1987, WITH 80% IGM,
- POSITIVE ANIMALS SINCE 1987.
AY IMPORTANT DECREASE IS OBSERVED WITH NOT NOTICEABLE VIRAL ACTIVITY IN THE
STUDIED SENTINEL LOCATIONS.
THE RAPID RENEWAL (TURN-OVER)
OF SMALL RUMINANT POPULATION, MIGHT BE AN
:
IMPORTANT FACTOR FOR THE RVFV ANTIBODY PREVALENCE DECREASE OBSERVED.
SLIDE 9
A NATIONAL RVFV PREVALENCE SURVEY CONDUCTED IN NOVEMBER 1987-
FEBRUARY 1988 IN SEVERAL PLACES AS INDICATED IN THE MAP SHOWED A NEGATIVE
GRADIENT FROM NORTH TO SOUTH (l9,2% IN THE NORTH, 8% IN THE CENTRAL AREAAND
2,3%IN THE SOUTH AREA).
NORTHERN AREA:ST-LOUIS, LOUGA ISOHYETE 300MM
CENTRALAREA: THIES, FATICK, KAOLACK DIOURBEL ISOHYETE 600MM
SOUTHERN AREA: TAMBACOUNDA,ZIGUNCHOR,
KOLDA ISOHYETE900MM
’
THE 1990 PREVALENCE OF RVFV ANTIBODY IN THE SENEGAL RIVER BASIN IS NOW
SIMILAR TO THE CENTRAL AREA PREVALENCE WHERE NO RVFV OUTBREAKS WERE
REPORTED, NEITHER IGM WERE DTECTABLE IN HUMAN AND ANIMAL POPULATIONS,
TRADUCING A LOW VIRUS ACTIVIN
IN OTHER AREAS (AS FERLO) WHERE PUNCTUAL SEROSURVEYS WERE CONDUCTED, A
DECREASE OF RVF VIRUS ACTIVITY WAS ALSO OBSERVED SINCE 1987.
LIGHT ON
IN 1988 RVFV ACTIVITY WAS STILL PRESENT IN SOUTHERN MAURITAN’A.
THE ACTUAL RVFV IMMUNITY LEVEL IN THE SENEGAL RIVER BASIN INCREASES THE RISK
OF OCCURENCE OF OTYER OUTBREAK.
THE ECOLOGICAL CHANGES IN THE SENEGAL RIVER BASIN WITH EXTENSIVE IRRIGATION
SCHEMES ATTRACT ANIMAL AND HUMAN POPULATIONS AND COULD INCREASE SUCH
RISKS.
THE SEROSURVEY WE PRESENTED WILL SE PURSUED
T:]E MAINTENANCE CYCLE OF RIFT VALLEY FEVER VIRUS IN WEST-AFRICA IS STILL
UNRESOLVED AND WILL NEED FURTHER INVESTIGATIONS WITH A MULTIDIMENSIONNAL
APPROACH LNCLUDING HUMAN SURVEY, CLIMATOLOGICAL, ENTOMOLOGICALAND
ECOLOGICAL
ASPECTS.
RVF virus IgG antibody prevalence in domes?ic
a n i m a i s i n S o u t h e r n Mauritania (1982-1985).
Anima!s
number
p o s i t i v e
%
tested
shs+
8 4
12
14,3
goais
262
4 2
16,O
cattie
6 2
8
12,9
Carne!s
5 8
19
32,8
Source: Saluxa et a!., Laricet 23.‘02;87
l *
. l . .*
.* .* .* . . . . . . . .
.
.
.
.
.
. . . . : . l .
Year
NO.
% poa. % DC.3
teskd
(ELISA)
(N’T)
UPPER BCS:N
1388
38
2 5 . 0
20.3
1989
5 5
15.1
14.5
139c
236
4.8
2.6
MICCCE BASLN
i3aa
170
18.9
19.4
1389
8 5
19.3
15.6
1990
2 5 3
15.8
10.5
LOï, ÉR BASiN
386
3 5
45,7
77.1
989
160
25.6
23.!
990
ion
9.c
9 . 0
TOIZ‘
388
2 9 3
23.9
22.3
389
3 2 4
f8.a
19.1
890
5 7 3
lC.5
7.0
.
?REVALE:KE OF RVFV A?iTIsOD” IN SMALL RUPIP4ANTS
FROM TiiC SENEGAL RIVER BASIN : 1988- 1990 (ELISA)
50
u
.
*
.
4 .
1
?
RVFV neutralizing antibody prevalence in small ruminants in the Senegal river
basin (1988-l 990)
Page 1
i
(RVF virus, Bunyaviridae genus Phlebovirus, is an arthropod-borne vira! disease
primarily affecting domestic animals, first isolated during an epizootic in 1930 in
Kenya.)
( in human, pathology was reported as an non-fatal febrile illness , but during the
!ast epizootics hemorrhagic fever syndroms and high fata!ity rate were observed.
Encepha!itis and chorioretinitis were atso observed. )
Egyp?: (80-700% of the ewes aborted, 860% of the adult animals died, and
mortaiity in the few lambs present approached 100%. )
(Severe clinical manifestations in human with high mortality rate were reported. )
( The question of endemicity of RVF virus in epizootics areas was unresolved and
needed definitive investigation.)
(in southern Mauritania with 15% positive domestic animal).
!gM anti bodies
detected in the sera of came! breeders indicated a recent circulation of ?he virus.
No correlation was observed in animais with reported abortion.
Saluzzo et al.
(1986) suggested that ample opportunity for epidemic-epizootic RVFV
?ransmiision existed in the Senegal River Basin of northern Senegal and
Sou?hern Mauritania.
1987 outbreak 385 cases reported (with 11% fatality rate) during an epizootic
among domestic ruminants. Strains of RVFV were iso!ated from people coming
:
from 225 kms (135 miles) east of Rosso and 6Qkms (35 miles) west of Rosso.
RVFV infected a high proportion of the domestic animais in the areas where
human disease reports were received. A much higher proportion of the animals
tested had RFV antibodies than tha? found among the human popuiation. This
once emphasizes the important role of domestic animals as amplifying hosts of
RVFV.
The ecological environment of the Senegal River Basin was recently
modified, in a large water conservation scheme, by the bulding of dams on the
Senegal river: in the Delta the Diama dam as a sait water barrier dam and in the
Upper curse in south-eastern Mali (Manantali dam). This possibly was an
additive factor in the occurence in the fal! of 1987. Developments in the areas
have encouraged migration and RVFV risk outbreak increased.
Results
Between the 1988- 1990 period , a significant decrease was giobaly observed
either by Elisa (24% in 1988 to 10,5% in 1990) or by neutralizaiion test
(X2= 29,76 ddl=2 p<O,OOl) was observed by Elisa and by NT (23 % in 1988,
19% in 1989 and 7% in 1990) (X2= 43,58 ddl=2 p<O,OOl )
A negative gradient from West to East was reported: by EL!SA: delta 46%,
middie basin 19% and Upper basin 25%
In the midd!e basin area, no significant variations of RVFV prevalence were
detected during the three year observation: 19 % in 1968 and 1989, 16% in 1990.
but by NT, significative variation X2= 7,88 ddl=2
We observed a similar pattern of antibody prevalence by neutralization test: a
high 1988 RVFV antibody preva!ence 77% in the lower basin, 19 % in the middle
basin and in the Upper basin:
( X2 = 70,7 ddl=2 p<O,OO!) between the 3
nreas). in the lower basin for the 3 years period the decrease is highly
significant. X2= 65,14 ddl=2 p ~0,001.
ovine-yoat : In 1990 non significant difference: X2= 0,56 ddl=l, with 6,6% positive
ovine and 7,2%caprine.
(in 1989, non significant difference: X2= 1,68 ddl=l )
juveniie , Young adults ( 2 to 6 adult teeth by jaw or moreless l to 3 ye;as-old) and
adults (8 teeth).
- in juveniles the percentage was significatively lower than in another age groups
(adults) In 1989 X2= 48,71 ddl=2 , in 1990 X2= 28,70 ddl = 2
The rapid renewal (turn-over) of small ruminant population, estimated in
sahe!ian conditions to about 50% animals one year old or less, is an important
factor for the RVFV prevalence decrease observed. In our samples, the Young age
group represented 33% of the total.
A national RVFV prevalence survey conducted in november 1987- february 1988
in several places as indicated in the map
northern area:St-Louis, Louga isohyete 300mm
central area: Thies, Fatick, Kaolack Diourbel isohyete 600mm
southern area: Tambacounda,Zigunchor, Kolda isohyete 900mm
T. The results prsented correlate with negative attempts of RVF virus isolations
from susceptible vectors collected in the delta area in the last 2 years, indication
of a viral low activity (1988-l 990).
SLIDE 1
TITLE AUTHORS
SL!DE 2
PREVALENCE iN SOUTHERN MAURITANIA 1985
SLIDE 3
MAP OF NORTH SENEGAL
SLIDE 4
1988-1990 SEROSURVEY RESULTS TABLE
SLIDE 5
GRAPHE ELISA REPARTITION BY AREAS
SLIDE 6
GRAPHE NEUTRALIZATION TEST REPARTITION BY AREAS
SCIDE 7
GRAPHE REPARTITION BY AGE GROUP AND SPECIES IN 89-90
SLIDE 8
GRAPHE COMPARISON OF PREVALENCE FROM 1982 TO 1990 LOWER BASIN
SLIDF 9
MAP OF SENEGAL; NATIONAL SEROSURVEY IN NOV :987-FE& 90
SLIDE 1
f’OST-EP!ZOOTIC PREVALENCE OF RIFT VALLEY FEVER ANTIBODY IN SMALL RUMINANTS
f:ROM THE SENEGAL RIVER BASIN (1988 -1990)
AUTHORS:
YAYA THIONGANE ISRA, H.G. ZELLER
PASTEUR INSTITUTE, H.G. FATY
AND J.A. AKAKPO, DAKAR UNfVERSITY VETERINARY SCHOOL, J.P. GONZALEZ, ORSTOM
THIS WORK IS PART OF A COLLABORATIVE STUDY BETWEEN THE SENEGALESE
!NSTITUTE FOR AGRICULTURE RESEARCH, THE PASTEUR INSTITUTE AND ORSTOM.
THE RIFT VALLEY FEVER IS AN ARTHROPOD-BORNE VIRAL DISEASE PRIMARLY
AFFECTING DOMESTIC ANIMALS AND SECONDARLY CAUSING SEVERE OUTBREAKS IN THE
HUMAN POPULATION OF AFRICA.
IT PRODUCES A ZOONOSIS AMONG RUMINANTS, CAUSING HEPATITIS WITH
YECROSIS, ABORTION IN ADULTS AND MORTALITY IN YOUNG OFFSPRING.
’
---IN EASTERN AFRICA, IN 1977 AND AGAIN, IN 1978, EXTENSIVE EPIZOOTICS OCCURRED IN
SEVERAL AREAS OF THE NILE DELTA AND VALLEY IN EGYPT.
--- AGA!N THE VIRUS WAS ISOLATED IN 1979 AND 1980 ALTHOUGH WIDESPREAD
EIPIZOOTICS DID NOT OCCUR IN THESE YEARS.
--IN WESTERN AFRICA, RVF VIRUS WAS ISOLATED FROM AEDES AEDlMORPHUS IN
BURKINA FASO IN 1983, FROM AEDES DALZIELI IN SOUTH-EAST PART OF SENEGAL IN
KEDOUGOU !N 1974 AN3 1983 AND FROM CUL!COIDES IN NIGERIA IN 1967.
SLIDE 2
IN 7985, A LARGE FOCUS OF RVF VIRUS CIRCULATION WAS IDENTIFIED IN THE SENEGAL
RIVET? AREA. (15% PREVALENCE AMONG DOMESTIC ANIMALS)
IGM ANTIBODIES DETECTED IN THE SERA OF CAMEL BREEDERS INDICATED A RECENT
CIRCULATION OF THE VIRUS.
DURING THE 1987 RAINY SEASON, EXTENSIVE EPIZOOTICS OF RVF VIRUS
OCCURED IN THE SENEGAL RIVER BASIN AMONG DOMESTIC RUMINANTS.
MOREOVER A TOTAL OF 385 HUMAN CASES WERE REPORTED IN MAURITANIA AT THE
ROSSO HOSPITAL .
AGAIN, IN OCTOBER 1988, AN ACTIVE CIRCULATION OF RVF VIRUS WAS OBSERVED IN
MAURITAN!A AND HERDS OF DOMESTIC ANIMALS SHOWED SIGNIFICANT PERCENTAGES OF
RVFV IGM.
THE OCCURENCE OF SUCH VIRAL MANIFESTATIONS PROMPTED US JO EVALUATE
THE DEGREE OF !MMUNITY AMONG SMALL RUMINANTS IN WHATAPPEARED TO BE A RISK
AREA
SL!DE 3
WE SJUDIED THE PREVALENCE OF RVFV ANTIBODIES !N SMALL RUMINANTS (SHEEP AND
GOATS) ALONG THE LEFT BANK OF THE SENEGAL RIVER BASIN.
THIIEE AHEAS WEHE DEFINED: ON THE MAP:
- UP?ER BASIN (MATAM), MIDDLE BASIN (PODOR) AND LOWER BASIN
(DAGANA).
SELECTED LOCATIONS WERE RANDOMLY CHOOSEN.
ANIMALS OF 2 OR MORE HERDS BY LOCATION WERE BLEEDED WITHOUT INDIVIDUAL
TAGGING.
SPEC!ES, SEX AND AGE (ADULT TEETH) OF THE ANIMALS WERE REPORTED, SO
ABORTIONS, HIGH MORTALIJY.. .
SERA WERE TESTED:
- PY FLISA (USING A HUMAN STRAIN FROM THE 1987 MAURITANIAN OUTBREAK) FOR IGG
AND IGM DETECTION
- AND BY NEUTRALIZATION TEST (USING THE VACCINE SMITHBURN STRAIN) IN TWO
DIFFERENT LABORATORIES AND RESULTS WERE COMBINED.
SLIDE 4
293 SERA FROM SHEEP AND GOA~S WERE COLLECTED IN AUGUST 1988,324 IN AUGUST
1989 AND 583 IN SEPTEMBER 1990
BETWEEN THE 1988- 1990 PERIOD , A SIGNIFICANT DECREASE WAS GLOÇIALY OBSERVED
EITHER BY ELISA (24% IN 1988 TO 10,5% IN 1990) OR BY NEUTRALIZATION TEST (23 % IN
1988 TO 7% IN 1990)
tN A MORE DETAILED ANALYSIS, WE OBSERVED A SIGNIFICATIVE DECREASE OF ANTIBODY
PR-VALENCE IN THE LOWER BASIN AND IN THE UPPER BASIN EITHER BY ELISAAND
NEUJRALIZATION TEST.
IN THE MIDDLE BASIN AREA, NO SIGNIF!CANT VARIATIONS OF RVFV PREVALENCE WERE
DETECTED DURING THE THREE YEAR OBSERVATION PERIOD BY ELISA :
19% IN 1988 AND 1989,16% IN 1990.
SLIDE 5
!N AUGUST 1988, AN HIGHER PREVALENCE WAS OBSERVED IN THE LOWER BASIN WHERE
THE ‘987 OUTBREAK OCCURED.
iN AUGUST 1989, A HIGHLY SIGNIFICANT DECREASE OF PREVALENCE IN THE LOWER BASIN
WAS OSSERVED : 45,7% IN 88, 25,6% IN 89, AND, AGAIN, IN 1990: 10,5%.
IN THE UPPER BASIN AREA THE DECREASE IS SIGNIFICANT IN THE PERIOD 1988-1990.
IN 1388, RVFV IGM WERE DETECTED IN 4 ANIMALS FROM THE THREE STUDIED AREAS.
IN 2 CASES, SERA WERE IGM POSITIVE, IGG NEGATIVE BY ELISA AND POSITIVE BY
NEUTRALIZATION TEST.
IN 1989, ONLY TWO IGM SERA WERE DETECTED (ONE FROM THE UPPER BASIN AND ONE
FROM THE MIDDLE BASIN).
AND IN 1990 AN ABSENCE OF RVFV IGM POSITIVE SERA
i)
SLIDE 6
A S’MILAR PATTEHN OF RVFV ANTIBODY PREVALENCE WAS OBTAINED BY
NEUTRALIZATION TEST :
THE 1968 HIGH PREVALENCE IN THE LOWER BASIN (77% VERSUS 46% BY ELISA)
A GLOBAL DECREASE OF ANTIBODY PREVALENCE ON THE 3 YEAR-PERIOD
AND A KITICEAELE DECREASE IN THE MIDDLE BASIN AREA (19% IN 1988,16% IN 1989 AND
11% IN 1990)
SLlDE 7
THE PREVALENCE OF RVF VIRUS ANTIBODY AMONG SMALL RUMINANTS SHOWED
NO S!C,Y!FICANT DIFFERENCES BETWEEN SHEEP AND GOATS.
HOWEVER, THERE WERE VARIATIONS OF PERCENTAGE OF POSITIVE ANIMALS BY AGE
GROUP:
JUVENILE, YOUNG ADULTS AND ADULTS.
IN JUVENILES THE PERCENTAGE WAS SIGNIFICATIVELY LOWER THAN IN ANOTHER AGE
GROUPS (ADULTS)
SLIDE 8
THE CC’>b!PARISON OF PRE- AND POST-EPIDEMIC RVF VIRUS IGG AND IGM ANTIBODY AS
SI-iOWN HERE AMONG r)OMESTIC ANIMALS IN THE LOWER BASIN OF THE SENEGAL RIVER
’
SMOWED:
- AN ABSENCE OF VIRAL ACVTIVITY IN 1982,
-A 3% PREVALENCE IN 1983 AND 85% PREVALENCE IN
NOVEMBER 1987, WITH 80% IGM,
- POSITIVE ANIMALS SINCE 1987.
AY IMPORTANT DECREASE IS OBSERVED WITH NOT NOTICEABLE VIRAL ACTIVITY IN THE
STUDIED SENTINEL LOCATIONS.
THE RAPID RENEWAL (TURN-OVER)
OF SMALL RUMINANT POPULATION, MIGHT BE AN
:
IMPORTANT FACTOR FOR THE RVFV ANTIBODY PREVALENCE DECREASE OBSERVED.
SLIDE 9
A NATIONAL RVFV PREVALENCE SURVEY CONDUCTED IN NOVEMBER 1987-
FEBRUARY 1988 IN SEVERAL PLACES AS INDICATED IN THE MAP SHOWED A NEGATIVE
GRADIENT FROM NORTH TO SOUTH (l9,2% IN THE NORTH, 8% IN THE CENTRAL AREAAND
2,3%IN THE SOUTH AREA).
NORTHERN AREA:ST-LOUIS, LOUGA ISOHYETE 300MM
CENTRALAREA: THIES, FATICK, KAOLACK DIOURBEL ISOHYETE 600MM
SOUTHERN AREA: TAMBACOUNDA,ZIGUNCHOR,
KOLDA ISOHYETE900MM
’
THE 1990 PREVALENCE OF RVFV ANTIBODY IN THE SENEGAL RIVER BASIN IS NOW
SIMILAR TO THE CENTRAL AREA PREVALENCE WHERE NO RVFV OUTBREAKS WERE
REPORTED, NEITHER IGM WERE DTECTABLE IN HUMAN AND ANIMAL POPULATIONS,
TRADUCING A LOW VIRUS ACTIVIN
IN OTHER AREAS (AS FERLO) WHERE PUNCTUAL SEROSURVEYS WERE CONDUCTED, A
DECREASE OF RVF VIRUS ACTIVITY WAS ALSO OBSERVED SINCE 1987.
LIGHT ON
IN 1988 RVFV ACTIVITY WAS STILL PRESENT IN SOUTHERN MAURITAN’A.
THE ACTUAL RVFV IMMUNITY LEVEL IN THE SENEGAL RIVER BASIN INCREASES THE RISK
OF OCCURENCE OF OTYER OUTBREAK.
THE ECOLOGICAL CHANGES IN THE SENEGAL RIVER BASIN WITH EXTENSIVE IRRIGATION
SCHEMES ATTRACT ANIMAL AND HUMAN POPULATIONS AND COULD INCREASE SUCH
RISKS.
THE SEROSURVEY WE PRESENTED WILL SE PURSUED
T:]E MAINTENANCE CYCLE OF RIFT VALLEY FEVER VIRUS IN WEST-AFRICA IS STILL
UNRESOLVED AND WILL NEED FURTHER INVESTIGATIONS WITH A MULTIDIMENSIONNAL
APPROACH LNCLUDING HUMAN SURVEY, CLIMATOLOGICAL, ENTOMOLOGICALAND
ECOLOGICAL
ASPECTS.
RVF virus IgG antibody prevalence in domes?ic
a n i m a i s i n S o u t h e r n Mauritania (1982-1985).
Anima!s
number
p o s i t i v e
%
tested
shs+
8 4
12
14,3
goais
262
4 2
16,O
cattie
6 2
8
12,9
Carne!s
5 8
19
32,8
Source: Saluxa et a!., Laricet 23.‘02;87
l *
. l . .*
.* .* .* . . . . . . . .
.
.
.
.
.
. . . . : . l .
Year
NO.
% poa. % DC.3
teskd
(ELISA)
(N’T)
UPPER BCS:N
1388
38
2 5 . 0
20.3
1989
5 5
15.1
14.5
139c
236
4.8
2.6
MICCCE BASLN
i3aa
170
18.9
19.4
1389
8 5
19.3
15.6
1990
2 5 3
15.8
10.5
LOï, ÉR BASiN
386
3 5
45,7
77.1
989
160
25.6
23.!
990
ion
9.c
9 . 0
TOIZ‘
388
2 9 3
23.9
22.3
389
3 2 4
f8.a
19.1
890
5 7 3
lC.5
7.0
.
?REVALE:KE OF RVFV A?iTIsOD” IN SMALL RUPIP4ANTS
FROM TiiC SENEGAL RIVER BASIN : 1988- 1990 (ELISA)
50
u
.
*
.
4 .
1
?
RVFV neutralizing antibody prevalence in small ruminants in the Senegal river
basin (1988-l 990)
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