Citation
Ziem, J. B. (2006, June 4). Controlling human Oesophagostomiasis in Northern Ghana.
Retrieved from https://hdl.handle.net/1887/4917
Version:
Corrected Publisher’s Version
Abstract
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Introduction
Infections with Oesophagostomum bifurcum and hookworm have been recognized as a major health problem in northern Ghana and Togo (Polderman et al., 1991). Although mass treatment with one of the broad spectrum anthelmintics is the obvious approach to control these infections, there has been little relevant experience and there are few data available on the efficacy of using singledose regimens against human O. bifurcum infections. After Krepel et al. (1993) conducted smallscale trials with albendazole, pyrantel pamoate, levamisole and thiabendazole, they concluded that albendazole (Zentel ® ; GlaxoSmithKline, Uxbridge, U.K.), in dosages of 400–800 mg, was most likely to give a parasitological cure of O. bifurcum infection. Albendazole is currently the drug of choice for the treatment of infections caused by hookworm and other intestinal nematodes in Ghana and is well tolerated when given in a single dose. In combination with ivermectin, it is now also used in the national Lymphatic Filariasis Elimination Project.
Subjects and methods
Study Area
The study was conducted in November–December 2002, in the Garu area of the Bawku East district of the Upper East region of northern Ghana. This area is known to be a focus of intense transmission of both O. bifurcum and hookworm (Storey et al., 2000a; Yelifari et al., 2004). The subjects of the present study came from a small number of hyperendemic villages around the town of Garu. These study villages lie close to the Togolese border, in a rural area 30 km to the south– east of the district capital, Bawku. Detailed descriptions of the geographical location and characteristics of this area and of the local epidemiology of both nematode infections will be given elsewhere.
Design
Compounds (each a cluster of households) were selected at random until the selected compounds together contained 200 residents. The potential subjects of the present study were the 190 residents of the selected households (which together represented 10% of those in the study villages) who were aged ≥3 years and not pregnant. Each of these 190 individuals agreed to participate in the study and was invited to submit two stool specimens for laboratory examination, one before albendazole treatment and one 21–28 days after.
Diagnosis and treatment of helminth infections
Each stool sample was checked for helminthes using a single, 25mg, Kato smear and at least two coprocultures. The Kato smears were examined 15 min after their preparation and the presence and numbers of ‘hookwormlike’ eggs were noted. Since hookworm and O. bifurcum eggs are morphologically identical, differential diagnosis had to be based on the coprocultures.
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Every subject was offered treatment, under supervision, with a single oral dose of 400 mg albendazole.
Data analysis
The intensities of infection among those found infected are presented as geometric mean egg counts (GMEC; as eggs/g faeces) and as geometric mean larva counts (GMLC; as the number of larvae in the two cultures set up, using a total of 4 g faeces, for each subject). The level of infection was also categorized by intensity class (see Tables). Cure ‘rates’ (CR) and egg/larvareduction ‘rates’ (ERR/LRR) were calculated as follows:
CR= [100 (No. positive before treatment no. positive after treatment)]. No positive before treatment.
ERR/LRR= [100(GMEC/GMLC before treatmentGMEC/GMLC after treatment)] GMEC/GMLC before treatment
Ethical Considerations
Witnessed, verbal, informed consent was obtained from all subjects. The head of each selected household and each subject asked to give a stool sample were asked verbally for their consent by one member of the research team. Each request for consent was witnessed by another team member. All subjects examined were offered and accepted albendazole treatment. Ethical clearance for the study was obtained from the Ministry of Health of Ghana and the project protocol was approved and recommended by the Danish Central Scientific Ethical Committee.
Results
Not all 190 subjects initially enrolled were successfully investigated by Kato smears and culture pretreatment and only 146 provided a posttreatment stool sample.
Pretreatment Survey
eggs were similar in the male and female subjects (data not shown). When examined by the coproculture method, 50 (34.2%) and 113 (77.4%) of the subjects examined were found infected with O. bifurcum and hookworm, respectively (Table 5.1). Although the thirdstage larvae of Strongyloides were also found in 32 (21.9%) of the subjects, no attempt was made to determine the response of these parasites to albendazole treatment. Again, no gender related differences were seen in either the hookworm or O. bifurcum infections (data not shown).
Table 5.1 Pretreatment prevalences and intensities of Oesophagostomum
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treatment but their GMEC decreased from 578 eggs/g pretreatment to 153 eggs/g posttreatment, giving an ERR of 73.5%. Cure ‘rates’, as determined from the smear data, were lowest among those subjects who appeared most heavily infected pretreatment (Table 5.2).
Discussion
The values of CR and ERR derived from the Kato smears in the present study were similar to those seen in several other investigations of albendazole treatment (Bennett and Guyatt, 2000), including the smallscale investigation of O. bifurcum infection conducted by Krepel et al. (1993), which was also based on Kato smears. In a recent review summarizing the results of several studies, Horton (2000) found that CR following albendazole treatment of hookworm are generally around 78%, although they may be as low as 33% and as high as 100%.
The use of coprocultures in the present study allowed the effects of albendazole to be evaluated separately for O. bifurcum and hookworm. The CR for O. bifurcum appeared to be very high, with only one of the 50 subjects who were found positive Table 5.3 Impact of the albendazole treatment on the hookworm infections, as
indicated by the results from the coprocultures
Pretreatment Posttreatment Effect of treatment
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prior to treatment still positive a few weeks posttreatment. With hookworm, on the other hand, the CR based on coproculture was disappointingly low when compared with that, based on the results of Kato analysis, reported by Krepel et al. (1993). In the present study, in terms of the prevalence of hookworm infection, the examination of Kato smears and the use of coprocultures gave similar results pre treatment but the posttreatment results for the two methods were markedly different. Following treatment, a subject was much more likely to be found infected with hookworms by coproculture than to be found smearpositive. The CR based on the results of examining Kato smears in which light infections are frequently missed, especially if only a single stool sample/subject is checked were therefore higher than those based on the coprocultures. In general, CR for hookworm may be severely overestimated if based solely on the results of Kato analysis. From a publichealth point of view, however, a failure to detect light hookworm infections in Kato smears is of little importance, since hookwormattributable morbidity is only usually observed with moderate or heavy infection. Encouragingly, the ERR/LRR of the present subjects who were most heavily infected with hookworms prior to treatment were >90%, whether these ‘rates’ were based on the results from the Kato smears or those from the coprocultures (data not shown).
It may be concluded that singledose treatment with albendazole, at 400 mg/ subject, results in a very high CR for O. bifurcum infections and a fairly low CR but high ERR for hookworm infections. Similar observations, albeit based on other methodologies and perhaps less clearcut, were made by Albonico et al. (1999) and Horton (2000). The efficacy of singledose albendazole against O. bifurcum, together with the limited geographical distribution of this nematode, indicates that mass treatment with the drug might not only result in significant reductions in the prevalence of O. bifurcum infection but also in the elimination of transmission. Control of human oesophagostomiasis through mass treatment would seem a realistic option.
Acknowledgement
