3

Click here to load reader

Efficacy of ivermectin in the treatment of concomitant Mansonella perstans infections in onchocerciasis patients

Embed Size (px)

Citation preview

Page 1: Efficacy of ivermectin in the treatment of concomitant Mansonella perstans infections in onchocerciasis patients

TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE (1993) 87, 227-229 227

Efficacy of ivermectin in the treatment of concomitant Mansonella perstans infections in onchocerciasis patients*

H. Schulz-Key’, W. Albrecht’, C. Heuschkel’, P. T. Soboslay’, M. Banla2 and H. G6rgen3 ‘Institute of Tropical Medicine, University of Tiibingen, Wilhelmstrasse 27, D-7400 Tiibingen, Federal Republic of Germany; 2Centre Hospitalier du Region Sokodi, Togo; 3German Association for Technical Co-operation (GTZ), Federal Republic of Germany

Abstract As part of an ivermectin dose-ranging study of onchocerciasis patients in Togo, 55 onchocerciasis patients with concomitant mansonelliasis received single oral doses either of ivermectin (100 to 200 yg/kg body weight) or placebo. As expected, Onchocerca volvulus microfilariae in the skin were greatly reduced in num- ber soon after drug treatment, but microfilariae of Mansonella perstans reacted differently. Microfilarial den- sities of M. perstans were assessed with a filtration technique both before, and 4 times after, treatment. In untreated patients microfilarial densities were stable until the end of the study at 6 months. In patients re- ceiving ivermectin, microfilarial densities dropped on average to less than 60% of the pre-treatment level and remained there until the final post-treatment examination. This partial reduction was probably not caused by a microfilaricidal effect of ivermectin, but rather by an altered distribution of microfilariae in the peripheral blood and in a suspected microfilarial reservoir.

Introduction Ivermectin is highly effective against a broad range of

nematodes of medical and veterinary importance, includ- ing most filarial worms. In patients suffering from on- chocerciasis, a single oral dose achieves rapid elimination and long-lasting suppression of skin microfilariae (AWADZI et al., 1986; HEUSCHKEL et al., 1989). Ivermec- tin has replaced diethylcarbamazine (DEC), and com- munity-based mass treatment campaigns against On- chocerca voZvulus were initiated bv the Onchocerciasis Control Programme (OCP) in West’Africa.

Ivermectin is believed to paralyse susceptible nema- todes by affecting neurotransmission mediated by y- amino-n-butvric acid (HOLDEN-DYE et al.. 19901. But total immob;lization 0; killing of microfilariae in vi&o has never been observed (MOSSI~GER et al., 1988; J~RGENS & SCHULZ-KEY. 1990‘1. and the exact mode of antifilarial ,, action remains unclear. Since ivermectin is microfilarici- da1 onlv and has a very short half-life in human plasma, the long-term suppression of microfilaridermia- in on: chocerciasis natients is difficult to understand. Even though a single dose had no macrofilaricidal efficacy, there is evidence that ivermectin affects adult 0. VOZVUZUS resulting in sequestrated microfilarial release from female worms (SCHULZ-KEY et al.. 1992). A close correlation between‘ changes in microf&ial release and the slow re- invasion of skin microfilariae could be demonstrated. However, the long-term effect of ivermectin cannot be explained bv this effect alone (SCHULZ-KEY 1990; SCHULZ-KE? et al., 1992). .

Microfilariae of Acanthocheilonema viteae were soon eliminated from Mastomys after treatment with ivermec- tin. Two months later sera from these animals were pas- sively transferred to other infected but untreated ani- maIs, and circulating microfilariae were again eliminated ~RAO et al.. 1987). These observations indicate that iver- mectin miiht noi act on the filarial parasite directly but, rather, through synergism with the host’s immune re- sponse (SCHULZ-KEY, 1987).

We expect further insight into the mode of action of ivermectin from studying its impact on other human and non-human filarial infections:, this study concentrates on the treatment of mansonelliasu.

Mansonella perstans is a frequent filarial parasite of man, yet it is rarely considered in public health pro- grammes since most infections remain asymptomatic. Symptoms, if present, are less spectacular and less spe- cific than those of other filarial infections. However, sev-

*Financial support was provided by the German Association for Technical Co-operation (GTZ), the Commission of the Euro- pean Communities, contract nos TSDl-002 and TSD-0066, the Onchocerciasis Chemotherapy Project (OCT) World Health Organization, contract no. 0111811203, and Merck Sharp & Dohme.

era1 authors have associated the presence of M. perstans microfilariae with generalized pruritus on the back and upper extremities, pain in the abdomen or joints, myo- cardiopathies, lymphoedema, elephantoid scrotum, or calabar swelhngs due to encapsulated nodules in the con- junctiva or eyelids (ADOLPH et al., 1962; ARENE & ATU, 1986; BAIRD et al., 1988; DUKES et al., 1968). These symptoms indicate the medical importance of this filarial infection and the need for its treatment (RICHARD- LENOBLE et al.. 1985: VAN HOEGARDEN et al.. 1987). Furthermore, &ultipie filarial infections are frequent in Africa, which means that symptoms of mansonelliasis may falsely be associated tiith- other filarial parasites. Treatment of multinle filarial infections mav result in severe adverse reactions (CHLEBOWSKY & %ELKE, 1980), which might cause complications in mass treat- ment campaigns against onchocerciasis.

In this study, we paid particular attention to those on- chocerciasis patients with concomitant mansonelliasis. As expected, 0. voZvulus microfilariae were drastically elimi- nated soon after drug administration, but microfilariae of M. perstans reacted in a completely different way.

Patients and Methods Selection of patients and parasitological assessment

The patients in this study came from 8 villages near Sokode in the arboreal Savannah of Togo, West Africa. Patients (182) heavily infected with 0. VOZVUZUS were se- lected for treatment with a single oral dose of placebo or loo., 150 or 200 kg ivermectin per kg body weight. All patients were admitted to hospital for an initial physical, parasitological and laboratory examination.

0. volvulus microfilarial density was assessed by 6 skin biopsies taken from the shoulders, hips and calves with a corheoscleral punch and incubatkd in saline for 24 h. For the detection of M. aerstans microfilariae. blood samples were collected and {he density of microfiiaraemia was quantitatively determined by blood filtration: one ml of venous blood was collected into a tube containing ethylendiaminetetraacetic acid, diluted with 4 ml saline, and passed through a polycarbonate filter (diameter 25 mm, pore size 3 pm). Five ml of saline and 10 ml of air were then passed through the same filter to wash off red blood cells and cause microfilariae to adhere to the filter. Subsequently the filter was placed on a slide, covered with 2 drops of saline and a cover slip. Microfila- riae, which were still motile, were counted with the acid of a microscope (100x).

To standardize the filtration technique, 5 ml samples of venous blood from patients with <ither low or gigh microfilarial densities were divided into 1 ml aliauots. The total number of microfilariae was assessed after fil- tration of each aliquot. The deviation of paired counts was less than 5% on average. In addition, the fractions

Page 2: Efficacy of ivermectin in the treatment of concomitant Mansonella perstans infections in onchocerciasis patients

228

strained through the filter were collected and centrifuged to assess how many microfilariae had been lost during fil- tration. More than 90% of the total number of microfila- riae in the blood sample were retained by a single filtra- tion.

Treatment of mansonelliasis patients As all patients with concomitant mansonelliasis were

integrated in the clinical studv of onchocerciasis, the drug administration was based-on the original protocol for onchocerciasis treatment. Fifty-five patients, from 77 detected cases, were finallv included in the studv of the efficacy of ivermectin against M, perstans. Since ti;e num- ber of patients treated with 100 or 200 hgikg (4 patients each) was rather small, we pooled all treated patients for the evaluation. Paired retrospective comparisons of the microfilarial densities before and after treatment con- firmed that this procedure was justified. It was also in ac- cordance with the experience available for ivermectin treatment of other filariases, using doses in this range.

Blood samples were collected before treatment and 3 d, 2-3 weeks, 4-7 weeks and 6 months after treat- ment

Results Onchocerciasis

Microfilarial densities in the skin dropped drastically within a few days to near zero, remaining there through- out the 6 months follow-up period.

Prevalence of mansonelliasis in untreated patients Mansonelliasis was highly prevalent in patients from

the 8 villages. Blood s&$le~ from 182 patients were examined and 77 142’3%) contained M. aerstans micro- filariae, with a raige of ‘1 to 3650iml blood. Six addi- tional patients, in whose blood microfilariae were not found at the first examination, revealed l-36 microfila- riae per ml at the 6 months follow-up. Only 2 patients, with one and 3 microfilariaeiml respectively at the first examination, did not reveal microfilariae at the 6 months examination.

Effect of ivermectin on microfilarial densities in the blood Fifty-five of the mansonelliasis patients were selected

to evaluate the filaricidal efficacv of ivermectin against M. perstans. Thirty-one were treated with the d&g (4 with 100 pglkg, 23 with 150 pgikg, and 4 with 200 ygikg), and 24 patients received placebo. Three days after treatment, microfilaraemia decreased signifi- cantly in 22 patients, but remained stable or even in- creased in the other 9. The overall mean level fell slightly (Figure). Thereafter, the number of circulating micro-

Figure. Changes of densities of circulating M. perstuns microfilariae in pa- tients treated with single oral doses of ivermectin or placebo and compari- son with the microfilaricidal efficacy of ivermectin in other human fiiariases. Ivermectin doses in each trial were as follows: M. perstuns, lOO- 200 &kg; W. banrrofti, 150 &kg; 0. volv~lus, 100-200 &kg; IA. loa, 200 pgikg. Data for patients with loiasis, bancroftian filariasis and on- chocerciasis were taken from our own observations and those of RICHARD- LENOBLE et al. (1989), CARTEL ef al. (1990, 1991), and HEUSCHKEL et al. (1989).

filariae declined further, stabilizing at the 2 weeks follow- up at a level less than 60% of the original value, and then remained unchanged until the final 6 months post-treat- ment examination. No correlation between the dose of ivermectin and changes in microfilarial densities was ob- served, but patients with lower microfilarial counts showed a relatively greater reduction than those with h&h microfilarial densities. However. onlv one of these 55-patients (with 3 microfilariae per rni befbre treatment) was microfilariae-negative at the 6 months post-treatment examination. In patients receiving placebo, microfilarial densities had sliahtlv, but not sirmificantlv, increased after 6 months ofobs&vation (Figure). ” .

Effect of ivermectin on microfilarial motility No difference was observed in the motility of micro-

filariae isolated from patients after treatment with iver- mectin or placebo. Also, changes of the typical nematode movement pattern, which had been described for iver- mectin-treated 0. volvulus microfilariae (M&SINGER et al., 1988; SOBOSLAY et al., 1987), could not be con- firmed for M. perstans.

Adverse reactions in patients with concomitant mansonelliasis In treated onchocerciasis patients, side reactions were

not clearly associated with the intensity of infection; moreover, they were often non-specific and unpre- dictable (HEUSCHKEL et al., 1989). We could not attrib- ute any adverse reaction equivocally to concomitant M. perstans infection. This was in accord with the poor microfilaricidal efficacy of ivermectin against M. perstans, and indicated that enhanced adverse reactions would be unlikely to complicate mass treatment campaigns using ivermectin against onchocerciasis.

Discussion Filaricidal efficacy of ivermectin against M. perstans

Previouslv. RICHARD-LENOBLE et al. 11989) treated 5 mansonellia& patients with low mic&l&~emia and concluding that ivermectin was ineffective against M. perstans. Despite a mean reduction of microfilarial counts by more than 40% in 31 patients (Figure), we were un- able to reach a conclusion concerning the possible micro- filaricidal efficacy of ivermectin, because it is not known whether this parasite has a microfilarial reservoir in its host. Hence, we could not be sure that microfilariae were actually destroyed and eliminated from the host.

For several species, such as Loa loa, Wuchereria ban- crofti, Dirofilaria immitis and A. viteae, microfilarial reser- voirs have been demonstrated in the lungs or other or- gans of the host, in which a significant proportion of the microfilariae are periodically, subperiodically, or perma- nently restrained. The density of circulating microfilariae is regulated by specific, but mostly unknown, mechan- isms (HAWKING, 1975; HAWKING et al., 1981). For M. perstans microfilariae, the size and location of the sus- pected reservoir are still unknown.

Blood-dwelling microfilariae in dogs infected with D. immitis were cleared or reduced by a partial exchange of peripheral blood, but within a few hours microfilarial densities had returned to the original level (PACHECO, 1974). On the other hand, soon after iniection of addi- tional microfilariae into already patently infected dogs, the maioritv of the ‘suoernumerarv’ microfilariae had been clkared from the peiipheral blood (PACHECO, 1914). A dynamic equilibrium between circulating and re- strained microfilariae was postulated,, evidently in- fluenced or regulated by host factors. Circulating micro- filariae were immediately replaced or removed according to this pre-set equilibrium. PACHECO (1974) suspected that, in patent infections, only a small proportion of D. immitis microfilariae were circulating, while the vast ma- jority remained in the reservoirs.

In animal loiasis, female worms start to release micro- filariae 4 months after infection. Initially, microfilariae are confined to the lymphatics and pulmonary circula-

Page 3: Efficacy of ivermectin in the treatment of concomitant Mansonella perstans infections in onchocerciasis patients

tion, and are not found in peripheral blood until 5-6 months later. Microfilaraemia increases to high levels, persists for some time, and subsequently declines to a low level without reduction of the microfilarial numbers in the lymphatics and pulmonary circulation (FINDER, 1988). Obviously, microfilariae find conditions more suitable in the reservoirs than in peripheral blood.

Hence, in the evaluation of drug effects, it must be considered that a significant but incomplete reduction of circulating microfilariae does not necessarily signify a major reduction of the whole parasite pool.

Since most of the microfilariae in a host may accumu- late in the reservoirs, we assume that ivermectin had no microfilaricidal effect on M. perstans, but rather inter- fered with factors influencing the size of the microfilarial reservoir and the distribution of circulating and retained microfilariae. This might also be true for other filariases which show incomplete or slow elimination of circulating microfilariae after treatment with ivermectin. Brugia mu- layi microfilariae in the leaf monkey were incompletely and variably cleared from peripheral blood (MAK et al., 1988). L. loa microfilarial numbers dropped to 12% of pre-treatment levels and remained low during the one month follow-up period (RICHARD-LENOBL~ et al., 19891. On the other hand a clear effect of ivermectin was repoited in a patient infected with M. ozzardi, whose microfilariae were rapidly cleared after a single treatment (NUTMAN et al., 1987). A similar clear reduction in microfilarial numbers was observed in bancroftian fila- riasis (CARTEL et al., 1990, 1991), which can be at- tributed to the microfilaricidal efficacy of the drug.

The inability to localize and isolate adult M. perstuns from patients hampers direct proof of a macrofilaricidal effect of ivermectin. Since the longevity and the repro- ductive biology of M. perstans are still unknown, whether ivermectin intereferes with the development of intra- uterine microfilariae in female worms, as was observed with 0. VOZVUZUS (SCHULZ-KEY, 1987), remains an open question. Also no indirect sign of a late macrofilariddal effect, e.g. delaved disauuearance of microfilariae from periphera blood, was apparent. In fact, microfilarial densities proved to be rather stable over a long period after the initial reduction.

Acknowledgements This study was supported by rhe Togolese Ministry of

Health. For their valuable assistance we are gratefully indebted to the staff members of the Institut Ernst Rodenwaldt, Lome, and of the hospital in Sokode. We thank Merck Sharp & Dohme for providing ivermectin.

References Adolph, I’. E., Kagan, I. G. & McQuay, R. M. (1962). Diag-

nosis and treatment of Acanthocheilonema perstans filariasis. AmericanJournal of Tropical Medicine and Hygiene, 11,76--88.

Arene, F. I. 0. & F. N. Atu (1986). Mansonella perstans micro- filaraemia among the Bori community in the Niger Delta area of Nigeria. Annals of Tropical Medicine and Parasitology, 80, 535-536.

Awadzi, K., Dadzie, K. Y., Schulz-Key, H., Gilles, H. M., Fullford, A. J. & Aziz, M. A. (1986). The chemotherapy of onchocerciasis. XI. A double-blind comparative study of iver- me&n, diethylcarbamazine and placebo in human onchocer- ciasis m northern Ghana. Annals of Troaical Medicine and

I 1

Parasitology, 80,433-442. Baird, J. K., Neafie, R. C. & Connor, D. H. (1988). Nodules in

the conjunctiva, bung-eye, and bulge-eye in Africa caused by Mansonella Derstans. American Yournal of Trobical Medicine and Hwiene.38: 553-557. ” ” *

Car&T, J. i.,‘Celerier, I’., Spiegel, A., Plichart, R. & Roux J. F. (1990). Effect of two successive annual treatments &:ith single doses of ivermectin on microfilaraemia due to Wuchere- ria bancrofti var. aacifica. Transactions of the Roval Societv of Tropical Aedicine’aniHygiene, 84,837-$39. * _j J

Cartel, J. L., Spiegel, A., Nguyen, L., Genelle, B. & Roux, J. F. (1991). Double blind study on efficacy and safety of single doses of ivermectin and diethylcarbamazine for treatment of

229

Polynesian Wuchereria bancrofti carriers. Results at six mon- ths. Tropical Medicine and Parasitolog)r, 42,38-40.

Chlebowskv, H. 0. & Zielke. E. (1980). Studies on Bancroftian filariasis ;n Liberia, West Africa IV. ‘Notes on side effects ob- served during a diethylcarbamazine treatment campaign in a rural area endemic for Wuchereria bancrofti and Onchocerca volvulus. Tropenmedizin und Parasitologic, 31, 339-344.

Dukes, D. C., Gelfand, M., Gadd, K. G., Clarke, V. De V. & Goldsmith, J. M. (1968). Cerebral filarlasis caused by Acan- thocheilonema perstans. Central AfricanJournal of Medicine, 14, 21-27.

Hawking, F. (1975). Circadian and other rhythms of parasites. Advances in Parasitology, 13, 123-182.

Hawking, F., Jennings, T., Louis, F. J. & Tuira, E. (1981). The mechanisms which affect the periodic cycle of Pacific Wuchereria bancrofti microfilariae. Journal of Helminthology, 55.95-100. --I-- ----

Heuschkel, C., Schulz-Key, H., Banla, M., GBrgen, H., Kllger, S., Klauss, V. & Awissi, D. (1989). Onchozerko- setherapie: ei,ce Langzeitstudie mit Ivermectin in Togo. Mit- teilunpen der Osterreichischen Gesellschaft fiir Troaenmedizin und Parastologie, 11, 81-88.

II .

Holden-Dye, L. & Walker, R. J. (1990). Avermectin and aver- mectin derivates are antagonists at the 4-aminobutyric acid IGABA) receutor on the somatic muscle cells of Ascaris: is this ;he site bf anihelmintic action? Parasitology, 101 265-271.

Jiirgens, S. & Schulz-Key, H. (1990). Effect of ivermectin on the vertical distribution-of Onchocerca volvulus microfilariae in the skin. Tropical Medicine and Parasitology, 41, 165-168.

Mak, J. W., Lam, I’. L. W., Noor Rain, A. & Suresh, K. (1988). Effect of ivermectin against suboeriodic Brwia malavi &fectjon in the leaf monkey, Presbyk cristata. P&asitolo& Research, 74,383-385.

M&singer, J., Schulz-Key, H. & Dietz, K. (1988). Emergence of Onchocerca volvulus microfilariae from skin snips before and after treatment of patients with ivermectin. Tropical Me- dicine and Parasitology, 39,313-316.

Nutman, T. B., Nash, T. E. & Ottesen, E. A. (1987). Ivermec- tin in the successful treatment of a patient with Mansonella oz- zardi. 7ournal oflnfectious Diseases. 156.662-665.

Pacheco; G. (1974). Relationship beiween the number of circu- lating microfilariae and the total population of microfilariae in a host. Journal OfParasitology, 60, 814-818.

Pinder, M. (1988). Loa loa-a neglected filaria. Parasitology Today, 4,279-284.

Rao, U. R., Chandrashekar, R. & Subrahamanyam, D. (1987). Effect of ivermectin on serum dependent cellular interactions to Dipetalonema viteae microfilariae. Tropical Medicine and Parasitology, 38, 123-127.

Richard-Lenoble, D., Kombila, M., Burnier, I. & Maganga, M. L. (1985). Filarioses au Gabon: traitement par le meben- dazole des filarioses B M. perstans et Loa loa. Bulletin de la So- ci&tg de Pathologie Exotique, 78,485-491.

Richard-Lenbole, D., Kombila, M., Chandenier, J. & Gaxotte, I’. (1989). Efficacite et tolerance de l’ivermectine (mectizan) prescit chez le sujet multifilarien (Loa loaionchocercose etiou M. perstans). Bulletin de la Soci& de Pathologic Exotique, 82, 65-71.

Schulz-Key, H. (1987). Ivermectin in the treatment of on- chocerciasis. In: ISI Atlas of Science: Pharmacology. Philadel- phia: Institute for Scientific Information, pp. 246-249.

Schulz-Key, H. (1990). Observations on the reproductive biol- ogy of Onchocerca volvulus. Acta Leidensia, 59,27-43.

Schulz-Key, H., Soboslay, I’. T. & Hoffmann, W. H. (1992). Ivermectm-facilitated immunity. Parasitology Today, 8, 152- 153.

Soboslay, I’. T., Newland, H. S., White? A. T., Erttmann, K. D., Albiez, E. J., Taylor, H. R., Wilhams, P. N. & Greene, B. M. (1987). Ivermectin effect on microfilariae of 0. volvulus after a single oral dose in humans. Tropical Medicine and Parasitology, 38, 8-10.

Van Hoegarden, M., Chabaud, B., Akue, J. I’. & Ivanoff, B. (1987). Filariasis due to Loa loa and Mansonellaperstans: dis- tribution in the region of Okondja, Haut-Ogoout Province, Gabon, with parasitological and serological follow-up over one year. Transactions of the Royal Society of Tropical Medicine and Hygiene, 81,441-446.

Received 13 February 1992; revised 8 July 1992; accepted for publication 29 July I992