EFFECT O F A SINGLE DOSE (600 MG) O F ALBENDAZOLE O N LOA LOA MICROFILARAEMIA
K A M G N O J . * & B O U S S I N E S Q M.*
S u m m a r y :
The problem of Loa-encephalopathy, which may occur after ivermectin treatment of patients harbouring high Loa microfilarial loads, might be solved if one could find a treatment regimen bringing about a significant but progressive decrease in the Loa microfilaraemia. A trial was performed in Central Cameroon, whose aim was to follow up for 1 0 months, and to compare the changes in the Loa microfilarial loads in two groups of patients, one treated with a single dose (600 mg) of albendazole (Alben®, SmithKline Beecham) given with fatty food, and the other treated with mebendazole (100 mg, twice a day, generic tablets) at a fasting state. The microfilarial loads remained stable in the mebendazole group, whereas a significant decrease in microfilaraemia was recorded in the albendazole group (initial median load: 2 3 0 microfilariae per 5 0 µl; median load ten months after: 8 4 microfilariae per 5 0 µl). This should encourage further trials to evaluate the effects and the safely of two- or three- day albendazole regimens in patients infected with Loa loa.
KEY WORDS : albendazole, loa loa, loiasis, onchocerciasis, clinical trial, ivermectin, side effects.
Resume : EFFET D'UNE DOSE UNIQUE D'ALBENDAZOLE (600 MG) SUR LA MICROFILARÉMIE À LOA LOA
la prise d'ivermectine peut induire, chez les sujets
hypermicrofilarémiques pour Loa loa, des réactions sévères à type d'encéphalopathie. Ce problème pourrait être résolu par l'administration préalable d'un traitement abaissant de manière progressive cette microfilarémie. Lors d'un essai mené au Cameroun, nous avons comparé l'évolution sur 10 mois de la microfilarémie à Loa loa dans deux groupes de patients, l'un traité par une dose unique ¡600 mg] d'albendazole (Alben®, SmithKline Beecham) associée à la prise d'aliments riches en graisse, et l'autre traité à jeun par mebendazole (100 mg deux fois par jour pendant trois jours sous forme de comprimés génériques). La microfilarémie, restée stable dans le groupe mebendazole, a en revanche significativement chuté dans le groupe traité par albendazole (médiane des charges initiales : 230 microfilaires par 50 ul ; médiane des charges 10 mois après traitement : 84 microfilaires par 50 Ul). Ce résultat devrait conduire à évaluer l'effet et la tolérance de traitements de 2-3 jours par albendazole chez des patients parasités par Loa loa.
MOTS CLÉS : albendazole, Loa loa, hase, onchocercose, essai thérapeutique, ivermectine, effets secondaires.
L
arge-scale ivermectin (Mectizan®) treatments against onchocerciasis are hampered in Central Africa b y the fact that the drug may induce encephalopathy in those persons harbouring high Loa loa microfilaraemia ( G a r d o n et al, 1997; B o u s s i n e s q et al, 1 9 9 8 ) . T h e pathological processes involved in these accidents are not well known, but ophthalmological examinations sug- gest that they may b e related to a massive paralysis o f the Loa microfilariae (mf) leading to obstructive phe- n o m e n a in the capillaries o f the brain (Fobi et al, 2 0 0 0 ) . If this is so, a means o f solving the problem would b e to give, systematically to the w h o l e popula- tion, a preliminary treatment that would bring about a slowly progressive d e c r e a s e in the Loa m f counts.Should such a regimen b e found, it would b e possible, after a given interval, to administer Mectizan® at the stan-
* Laboratoire mixte IRD-CPC d'Épidémiologie et de Santé publique, Centre Pasteur du Cameroun, BP 1274, Yaoundé, Cameroun.
Correspondence: M. Boussinesq.
Tel.: (237) 223 35 84 - Fax : (237) 223 15 64.
E-mail : boussinesq@pasteur.cm
dard dose without having to implement specific sur- veillance procedures to monitor the serious reactions.
Our objective was to evaluate w h e t h e r a single d o s e o f a l b e n d a z o l e c o u l d b e used for such a preliminary treatment. T h e c h o i c e o f this drug and o f its d o s e was b a s e d o n four reasons: a ) the only study published s o far o n the effect o f albendazole o n Loa has s h o w n that repeated treatments with 2 0 0 mg during 21 days lead to a d e c r e a s e o f 8 0 % in the Loa m f counts after six months (Klion et al, 1 9 9 3 ) ; b ) trials have s h o w n that a single d o s e o f a l b e n d a z o l e ( 4 0 0 or 6 0 0 m g ) brings about a progressive decrease in the mf loads o f Wuche-
reria bancrofti (Ismail et al, 1998; D u n y o et al, 2000a, 2 0 0 0 b ) ; c ) the decision by SmithKline B e e c h a m Labo- ratories to donate albendazole for eliminating lymphatic filariasis (Sharp, 1998) suggests that the drug might also b e m a d e available free o f charge to facilitate the deve- lopment o f onchocerciasis control programmes in areas w h e r e specific p r o b l e m s associated with c o - e n d e m i c loiasis might b e e n c o u n t e r e d ; d) the c h o i c e o f a single d o s e was b a s e d on the fact that it would b e easily administered o n a large scale.
Article available athttp://www.parasite-journal.orgorhttp://dx.doi.org/10.1051/parasite/200209159
In a preliminary trial, a single d o s e (600 m g ) o f alben
dazole had b e e n administered at a fasting state to 17 children with Loa m f in the b l o o d . R e p e a t e d b l o o d e x a m i n a t i o n s up to 220 days after treatment did not s h o w any d e c r e a s e in the m f loads, w h e n c o m p a r e d with the pre-treatment values. As it is k n o w n that a fatty meal increases markedly the absorption o f alben
dazole (Lange et al, 1 9 8 8 ; Awadzi et al, 1 9 9 4 ) , a s e c o n d study was performed o n two groups o f loiasis patients, o n e treated with a single d o s e o f 600 mg o f a l b e n d a z o l e given with fatty food, and the s e c o n d receiving m e b e n d a z o l e in a fasting state. W e report here the results o f this study.
MATERIALS AND METHODS
T
h e trial was c o n d u c t e d in C a m e r o o n in two villages l o c a t e d about 6 0 km south o f Y a o u n d e . Standardized b l o o d films ( 5 0 ul) w e r e prepared b e t w e e n 1 1 . 0 0 a.m. and 1.00 p.m. from 2 7 7 persons aged 12 years and a b o v e . After Giemsa-staining, the Loa m f in the b l o o d films w e r e c o u n t e d . A total o f 45 p e r s o n s with m o r e than three Loa loa m f / 5 0 ul b l o o d a c c e p t e d to participate in the trial. T h e y w e r e divided into t w o groups, after stratification for m f concentrations. O n e group ( 2 4 patients) was given, in a fasting state, a three-day course o f m e b e n d a z o l e ( 1 0 0 mg, twice a day, in generic tablets). This drug was c h o s e n b e c a u s e it w a s m o s t u n l i k e l y to p r o d u c e changes in Loa microfilaraemia, while bringing a benefit to the patients by eliminating their intestinal nematodes, w h i c h are highly prevalent in the study area. T h e s e c o n d group ( 2 3 patients) received a single d o s e o f 6 0 0 mg o f albendazole (1.5 tablet o f Alben®, SmithK- line B e e c h a m ) , w h i c h was given together with o n e wheat fritter o f 4 5 - 5 0 g filled with s o m e 25 g o f butter.
This meal was c h o s e n b e c a u s e it is very c o m m o n l y eaten by the local population, and it allowed us to stan
dardize the quantity o f fat taken by the patients. T h e Loa m f l o a d s w e r e r e - m e a s u r e d , u s i n g t h e s a m e methods as at the initial examination round, 1, 7, 15, 30, 6 0 , 9 0 , 120, 150, 180, and 3 0 0 days after treatment.
T h e slides w e r e e x a m i n e d after e a c h examination, to determine w h e t h e r a m a r k e d d e c r e a s e in microfila
raemia would allow us to stop the trial; but for the final analyses, all the slides w e r e r e - e x a m i n e d at the e n d o f the trial, after having b e e n r e c o d e d so that the microscopist had n o information o n the patient's iden
tity o r the date o f b l o o d collection.
T h e analysis c o m p a r e d first the results o b t a i n e d in the two groups, using the W i l c o x o n - M a n n - W h i t n e y test.
T h e W i l c o x o n signed rank test w a s performed to eva
luate the c h a n g e s over time in the microfilaraemia. A 5 % significance level was used in all comparisons.
RESULTS
T
h e two groups o f patients did not differ significantly with regard to s e x ratio, average age, and pre-treatment m f counts. T h e initial median m f loads in the a l b e n d a z o l e and m e b e n d a z o l e groups w e r e 2 3 0 m f / 5 0 ul (range: 7 - 1 3 7 7 ) and 1 9 9 m f / 5 0 pi (range: 3 - 5 5 3 5 ) , respectively. T h e table I s h o w s the n u m b e r o f patients present, and the medians, ranges and Williams g e o m e t r i c m e a n s ( W G M ) o f the m f loads r e c o r d e d at e a c h examination; the W G M is the g e o metric m e a n calculated after having a d d e d 1 to e a c h count, in order to take into account the negative values (Williams, 1 9 3 7 ) . As several patients missed s o m e o f the examinations, w e c o m p a r e d , for e a c h round, the pre-treatment m f counts o f the patients o f both groups present at that round. At all the examinations, the t w o groups remained c o m p a r a b l e in terms o f initial levels o f microfilaraemia.
T h e c o m p a r i s o n s b e t w e e n g r o u p s did not s h o w a n y s i g n i f i c a n t d i f f e r e n c e at a n y o f t h e e x a m i n a t i o n r o u n d s ( T a b l e I ) . B u t w h e n analysing e a c h g r o u p separately, it w a s f o u n d that in t h e m e b e n d a z o l e g r o u p t h e m f l o a d s r e c o r d e d at e a c h p o s t - t r e a t m e n t r o u n d did not differ significantly w h e n c o m p a r e d with t h e values at DO, w h e r e a s in t h e a l b e n d a z o l e g r o u p the l o a d s r e c o r d e d at D 7 , D 1 5 and D 3 0 w e r e similar to t h e initial values, but t h o s e found from D 6 0 to D 3 0 0 w e r e significantly l o w e r . F r o m D 3 0 to D 1 8 0 , t h e m e d i a n l o a d in t h e a l b e n d a z o l e g r o u p d e c r e a s e d p r o g r e s s i v e l y from 3 0 4 to 8 6 m f / 5 0 pi. T h e n , the l o a d s s e e m e d to r e m a i n s t a b l e , with a m e d i a n value o f 8 4 m f / 5 0 pi at D 3 0 0 . Amongst the 2 3 patients w h o r e c e i v e d a l b e n d a z o l e , 14 p r e s e n t e d m f c o u n t s b e l o w 50 % o f the initial value at at least o n e follow-up e x a m i n a t i o n . A fall o f this m a g n i t u d e w a s o b s e r v e d o n o n l y n i n e o f t h e 2 4 p e r s o n s treated with m e b e n d a z o l e .
DISCUSSION
I
t has b e e n s h o w n that albendazole is neither macro- nor microfilaricidal for Onchocerca volvulus, but that the drug has an e m b r y o t o x i c effect o n all the intra-uterine stages, including the stretched m f (Awadzi et al, 1 9 9 1 ) - T h i s w o u l d e x p l a i n t h e p r o g r e s s i v e d e c r e a s e in O. volvulus m f loads, w h i c h w o u l d b e the result o f natural death o f m f and the interruption o f production o f n e w m f by the adult worms. With regard to W. bancrofti, it has b e e n s h o w n that daily d o s e s o f 8 0 0 mg repeated during three w e e k s have both micro- and macrofilaricidal effects ( J a y a k o d y et al, 1 9 9 3 ) . Although little is k n o w n o f the effect o f a single d o s e o f a l b e n d a z o l e o n W. bancrofti, s o m e results suggestALBENDAZOLE AND LOA LOA MICROFILAREMIA
that it could have an effect on the production o f m f b y the adult w o r m s ( D u n y o et al, 2 0 0 0 b ) .
In our study w e decided, for ethical reasons, to use m e b e n d a z o l e as a "control" treatment, having little effect o n the Loa microfilaria] load; and the stability in t h e m f loads r e c o r d e d in the m e b e n d a z o l e g r o u p s h o w e d that this decision was justified. T h e comparison b e t w e e n the two groups did not reveal a significant difference at any time after treatment, but this is pro
b a b l y related to the small n u m b e r o f patients enrolled in the study. In contrast, the fact that there w e r e dif
ferent patterns in the c h a n g e s r e c o r d e d in the two groups suggests that a single d o s e o f a l b e n d a z o l e given with a fatty meal brings about, in s o m e , but not all patients, a m a r k e d d e c r e a s e in the Loa microfila- raemia.
Striking differences in the r e s p o n s e s w e r e o b s e r v e d b e t w e e n individuals in the a l b e n d a z o l e group. T h e m f densities o f s o m e o f them d e c r e a s e d by m o r e than 10- fold, as c o m p a r e d with the pre-treatment values, w h e reas others s h o w e d very stable microfilaraemias such as t h o s e demonstrated in untreated patients (Garcia et al, 1 9 9 5 ) . T h e s e variations d o not s e e m to b e related to the s e x , the age, o r the initial level o f infection o f the patients; they c o u l d b e due to differences in the absorption o f the drug.
It is clear, from our results, that preliminary distribu
tions o f single d o s e s o f a l b e n d a z o l e would not b e a m e a n s to reduce, in a community, the Loa m f loads to such low values that ivermectin could b e then given without risk. T h e inter-individual variability in the effect o f the drug, and the relatively limited reductions o b s e r v e d in t h o s e patients w h o "responded" to treat
ment, are the main reasons for that. Although there was a significant d e c r e a s e in the median o f the Loa micro- filaraemia in the a l b e n d a z o l e group, the g e o m e t r i c m e a n s w e r e not r e d u c e d markedly. This is probably related to the fact that there w e r e still s o m e very high values in the a l b e n d a z o l e group at the end o f the follow-up. However, the observations reported in the present paper should e n c o u r a g e further trials, w h e r e the effects o f two- or three-day r e g i m e n s o f albenda
zole could b e tested. During the present study, n o reac
tion w a s recorded, e v e n in patients with very high m f counts, but B l u m et al. ( 2 0 0 1 ) reported recently a c a s e o f e n c e p h a l o p a t h y w h i c h o c c u r r e d on the third day o f an albendazole treatment in a patient harbouring a low Loa microfilaraemia ( 1 5 2 mf/ml). This event should lead to further c l o s e monitoring in order to evaluate the safety o f a l b e n d a z o l e in patients infected with Loa loa.
T h e m e c h a n i s m s b y w h i c h a l b e n d a z o l e reduces the Loa microfilaraemia is not k n o w n , but the slow rate o f m f reduction o b s e r v e d in C a m e r o o n and in B e n i n (Klion et al, 1 9 9 3 ) , and the observations made o n o t h e r filarial s p e c i e s , suggest that the drug is not ' Comparison between initial microfilaraemia and the values recorded at each post-treatment examination (Wilcoxon signed rank test); * shows the significant results (P < 0.05). b Comparison between the values recorded in the albendazole and the mebendazole groups at each examination (Wilcoxon-Mann-Whitney U test). Table I. - Median, first and third quartiles, Williams Geometric mean (WGM) and range of Loa loa microfilaraemia (microfilariae per 50 pi) in the groups treated with albendazole (600 mg) + fatty food, or with mebendazole (600 mg) in a fasting state.
microfilaricidal, b u t acts either o n the longevity, o r o n the reproductive capacities o f t h e adult w o r m s . This is an important point to consider b e c a u s e , in such a c a s e , t h e d e c r e a s e in t h e m f loads w o u l d then b e per- ceptible only after a given delay, which, as emphasized by Cline et al. ( 1 9 9 2 ) , w o u l d mainly d e p e n d o n t h e lifespan o f the mf: the longer this is, t h e later w o u l d its effect b e perceptible.
Concerning Loa loa, information o n m f lifespan is very scarce. It is k n o w n that Loa m f c a n survive for m o r e than 21 days in b l o o d b a n k e d at 1-6° C ( A u B u c h o n &
Dzik, 1 9 8 3 ) . B e s i d e s this, several attempts have b e e n m a d e to transfer Loa m f to uninfected hosts: Fulleborn ( 1 9 0 8 ) performed such e x p e r i m e n t s with dogs, a n d found that t h e m f h a d disappeared after o n e month, w h e r e a s G ô n n e r t ( 1 9 4 2 ) , having injected Loa m f from a C a m e r o o n i a n patient into himself, did n o t find the mf in his b l o o d at t h e third day after injection. More interesting information c o u l d b e drawn from the stu- dies performed b y D u k e ( I 9 6 0 ) , w h o followed u p the course o f infection in drills experimentally infected with h u m a n Loa, a n d then s p l e n e c t o m i z e d . Following the removal o f t h e spleen, an organ w h i c h suppresses the Loa m f from t h e peripheral b l o o d in m o n k e y s , the author o b s e r v e d a rapid rise in the m f densities, which r e a c h e d a plateau s o m e six months after the operation.
O n e m a y assume that at that time, there w a s an equi- librium b e t w e e n the newly produced m f a n d those dying from old age, and that the lifespan o f the Loa mf is in the order o f six months. This estimate would b e useful as part o f the further trials to detennine whether two- o r three-day regimens o f albendazole might finally solve the problem o f ivermectin-induced Loa e n c e p h a - lopathy. Should the results b e conclusive, they would give information o n the interval o f time to b e respected b e t w e e n the albendazole and the ivermectin treatments.
ACKNOWLEDGEMENTS
W
e are grateful to the populations o f Z o a - toupsi a n d A v e b e , w h o a c c e p t e d to partici- pate in the trial. W e wish to thank the staff o f Centre Pasteur w h o c o l l e c t e d a n d e x a m i n e d the samples. W e are grateful to Dr. B.O.L. D u k e for criti- cally reading o f t h e manuscript. This study w a s sup- ported b y t h e Institut d e R e c h e r c h e pour le D é v e l o p - p e m e n t (IRD, e x - O r s t o m ) .REFERENCES
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Reçu le 20 juin 2001 Accepté le 3 octobre 2001
