Annual mass treatment with albendazole might eliminate human oesophagostomiasis from the endemic focus in northern Ghana

As a follow-up to the study by Ziem et al., in this issue, efforts to control human oesophagostomiasis and hookworm infections in northern Ghana were pursued, and the results evaluated in collaboration with the Lymphatic Filariasis Elimination Programme. This phase of evaluation of the impact of mass treatment was no longer limited to a small-scale research setting: it was done both in the context of an operationally viable national control programme and as a continuation of the Oesophagostomum Intervention Research Project (OIRP). The methods of evaluation included classical stool examination with Kato thick smears, stool culture and ultrasound examination of the colon wall. The results showed that yearly population-based albendazole-ivermectin treatment in 11 villages scattered over north-eastern Ghana, with a treatment coverage of 70-75%, resulted in a reduction of Oesophagostomum prevalence from about 20% pre-intervention to less than 1% after 2 years of mass treatment. Simultaneously, hookworm prevalence went down from 70% to approximately 15%. The data, however, cannot be readily compared with those of Ziem et al. because of the relatively crude diagnostic (single stool cultures) screening system that had to be used for the evaluation of the large-scale control programme. In the research area of the OIRP, interruption of mass treatment resulted in a rising hookworm prevalence. The Oesophagostomum prevalence, on the other hand, continued to go down. Transmission of human oesophagostomiasis appears interruptible and small numbers of persistent cases of Oesophagostomum infection were shown insufficient to serve as a nucleus of renewed spread of the infection. The data suggest that both the infection with and the pathology due to human oesophagostomiasis can be eliminated and that elimination is likely to be achieved through operationally feasible albendazole-ivermectin treatment as used by the Global Alliance for the Elimination of Lymphatic Filariasis.

Distribution of human Oesophagostomum bifurcum, hookworm and Strongyloides stercoralis infections in northern Ghana

A cross-sectional study was carried out in 216 randomly selected, representative rural villages in the northeastern part of Ghana from March 1995 to May 1998. Inhabitants of randomly selected households, stratified by age and gender, were included. The geographical position of villages was recorded with a global positioning system (GPS). The prevalence of Oesophagostomum, hookworm and Strongyloides stercoralis infections in a study population of 20250 people was determined by microscopic examination of larvae in stool cultures. The overall prevalence was 10.2, 50.6 and 11.6% for the three nematodes, respectively. Hookworm infections were seen in all but one (99.5%) and S. stercoralis in 88.4% of the 216 villages, while Oesophagostomum infections were found to be common in a limited area with prevalences varying from 0 to 75%. An association was found between Oesophagostomum and hookworm infection, both at the individual and at the village level. Spatial analysis of the prevalence data indicated that the endemic area is relatively clearly demarcated to the south of the study area.

Ultrasonographic detection and assessment of preclinical oesophagostomum bifurcum-induced colonic pathology

In northern Ghana and Togo, Oesophagostomum bifurcum infects an estimated 250,000 people, as determined by cultures of stool samples. The juvenile stages of the helminth develop within colonic wall nodules, causing Dapaong tumor or multinodular disease, at the rate of 1 case per week at Nalerigu Hospital in Ghana. Our aim was to discover whether suspected colonic-wall pathology is ultrasonographically visible in asymptomatic individuals living in the area where O. bifurcum is endemic. A total of 464 persons from 3 villages, ranging from highly infected to noninfected, were examined with ultrasonography. Anechogenic colonic lesions with posterior wall enhancement were observed in 71 (54.2%) of 131 and 57 (24.5%) of 233 persons from the villages of endemicity, and no lesions were seen in persons from the village outside the area of endemicity. We describe the lesions noted in this study as nodules caused by O. bifurcum, on the basis of their association at a population level with prevalence of larvae in stools, their expected ultrasonographic appearance and distribution (on the basis of our surgical experience with oesophagostomiasis), and the lack of a convincing differential diagnosis.

Human oesophagostomiasis: a histomorphometric study of 13 new cases in northern Ghana

Oesophagostomiasis is an infrequently described and recognised parasitic infection in humans, caused by Oesophagostomum bifurcum. Although the disease is most often found in the northern part of Togo and the neighbouring part of Ghana, sporadic cases have been described in other parts of Africa and in Asia and South America: Uganda, Ivory Coast, Sudan, Kenya, Ethiopia, Indonesia, Malaysia and Brazil. Infection probably occurs by way of the ingestion of L3 larvae. These larvae penetrate the intestinal wall, especially that of the colon. Some of these larvae develop into young adult worms and return to the bowel lumen. Other larvae, however, develop into immature worms, which fail to settle in the lumen, forming abscesses in the bowel wall and causing pathology. In the literature 105 human cases have been described, many originating in the northern regions of Ghana and Togo. The present study was performed to evaluate 13 new cases originating in the northern part of Ghana (7 female and 6 male patients, aged between 2 and 60 years). Histopathologically, the patients could be divided into two groups: the first group showed multinodular disease, while patients in the second group presented with a single, nodular mass. In the first group, abscesses were seen throughout the colonic wall. The mean size of the cavities was 4.3+/-0.7 mm. There was no relation between the size and the localisation in the colonic wall. Abscesses were significantly larger in male patients than in female patients. There was no correlation with age. In the second group, histopathological examination showed a cyst of variable wall thickness with very limited inflammation. These cysts represented older lesions, often encapsulated in the mesentery. In conclusion, in this study we present 13 new cases of human oesophagostomiasis. The abscess formation was found to be organ specific, independent of age, and gender-related, producing a more intense tissue reaction in male patients.

The role of pigs as transport hosts of the human helminths Oesophagostomum bifurcum and Necator americanus

We conducted a study in an endemic area of both Oesophagostomum bifurcum and Necator americanus in northern Ghana to examine the possibility of pigs acting as transport hosts for these two human helminth species, due to the commonly observed coprophagic habits of pigs. Under controlled conditions four parasite-free pigs consumed fresh faeces from people heavily infected with both helminths, and faeces were subsequently collected from the rectum of the pigs from 5 to 50 h post-feeding. Four to five per cent of the O. bifurcum and N. americanus eggs fed to the pigs were viable and retrieved as third-stage larvae after coproculture of the pigs' faeces. We discuss the possible impact of the coprophagic habits of pigs as potential parasite transport hosts during different seasons in this area of West Africa.

Prevalence and distribution of gastro-intestinal helminths and haemoparasites in young scavenging chickens in upper eastern region of Ghana, West Africa

We conducted a cross-sectional study to determine the prevalence and species of gastro-intestinal helminths and haemoparasites in 100 chickens kept under extensive management systems in Ghana, West Africa. All the examined chickens (100%) were infected with gastro-intestinal helminths; a total of 18 species were detected. The species and their prevalences were: Acuaria hamulosa (25%), Allodapa suctoria (20%), Ascaridia galli (24%), Capillaria spp. (60%), Choanotaenia infundibulum (13%), Gongylonema ingluvicola (62%), Heterakis gallinarum (31%), H. isolonche (16%), Hymenolepis spp. (66%), Raillietina cesticillus (12%), R. echinobothrida (81%), R. tetragona (59%), Strongyloides avium (2%), Subulura strongylina (10%), Tetrameres fissispina (58%), Trichostronygylus tenuis (2%), and finally one unidentified acanthocephalan (1%) and one unidentified trematode (1%). Thirty-five per cent of the chickens were infected with the haemoparasites Aegyptinella pullorum and Plasmodium juxtanucleare (prevalences 9% and 27%, respectively). Association between chicken sex and prevalences was not significant. An over-dispersed distribution was seen for most of the helminth species.

Clinical epidemiology and classification of human oesophagostomiasis

The intestinal helminth Oesophagostomum bifurcum is highly and focally endemic in northern Ghana and Togo, and its juveniles produce a nodular inflammatory response as they develop in the intestinal wall. This pathology can produce clinical symptoms. We report on 156 cases of oesophagostomiasis presenting in 1996-98 to Nalerigu hospital in northern Ghana. The disease accounted for 0.2% of the out-patient department new presentations (about 1 patient per week), and 1% (16) of the major acute surgical cases. Children aged 5-9 years were most commonly affected. Multinodular disease (13% of the cases) results from hundreds of pea-sized nodules within the colon wall and other intra-abdominal structures, and presents with general abdominal pain, persistent diarrhoea and weight loss. Dapaong tumour (87%) presents as an abdominal inflammatory mass often associated with fever. The 3-6-cm tumour is painful, well-delineated, smooth, spherical, 'wooden', periumbilical, and adhered to the abdominal wall. Cases most commonly presented during the late rains and early dry season. Diagnosis by ultrasound has reduced the need for exploratory surgery, and the ability to sonographically evaluate conservative treatment with albendazole has curtailed management by colectomy or incision and drainage.

Parasites in cross-bred pigs in the Upper East region of Ghana

A cross-sectional study was carried out in the Upper East Region (UER) of Ghana in order to estimate the prevalence of parasitic infections in local cross-bred pigs. Out of 60 villages with a human population of 200-1000 inhabitants, 10 villages were randomly selected for the study. The number of pigs varied from 50 to 200 pigs per village. In total 259 faecal samples from growers were collected and examined. Ninety-one percent of the animals excreted parasite eggs. Among these the prevalence of Eimeria spp. was 77.2%, Isospora suis (27%) and Balantidium coli (19.3%).The following helminth eggs were identified: Metastrongylus salmi (19.3%); Physocephalus sexalatus (17.4%); Oesophagostomum spp./Hyostrongylus rubidus (60.6%); Trichuris suis (4.6%); Ascaris suum (12.7%); Ascarops strongylina (8.1%); Brachylaemus suis (1.9%); Paragonimus suis (0.8%); Globocephalus urosubulatus (2.7%); and Schistosoma suis (0.4%). Furthermore, six growers were selected from each village for clinical and postmortem examinations, i.e. 60 in total. The clinical examinations revealed ectoparasites on 98.3% of the animals. The ectoparasites were: Haematopinus suis (66.7%); Boophilus spp. (58.3%); Amblyomma spp (45.0%); Sarcoptes suis (38.3%); and Rhipicephalus spp. (8.3%). All pigs were examined for the presence of haemoparasites. It was found that 23.3% of the animals had haemoparasites. These were: Babesia perroncitoi (23.3%); Babesia trautmanni (13.3%); and Eperytrozoon suis (1.7%). Based on postmortem examinations the following adult worms were identified: Metastrongylus salmi (83.3%); Oesophagostomum dentatum (63.3%); Oesophagostomum quadrispinulatum (38.3%); Hyostrongylus rubidus (23.3%); Ascarops strongylina (76.7%); Globocephalus urosubulatus (20.0%); Strongyloides spp. (1.7%); and Physocephalus sexalatus (65.0%). Cysts of the human tapeworm Taenia solium, Cysticercus cellulosae, were present in 11.7% of the animals. Small pieces of the diaphragm were examined for the presence of Sarcocystis spp.. The prevalence was 28.3%, but no larvae of Trichinella spp. were found. Furthermore, four of the animals (6.7%) had Taenia hydatigena cysts.

The intermediate hosts of Dracunculus medinensis in northern region, Ghana

Cyclopoid copepods were collected over a period of 17 months from six man-made water reservoirs in an area of northern Ghana where dracunculiasis is endemic. The numbers and species of cyclopoid copepods as well as the species naturally infected with Dracunculus medinensis larvae were recorded at fortinightly intervals. The occurrence of copepods was compared with concurrent rainfall and with monthly incidences of dracunculiasis in the year after the reservoir survey. Seven species and two subspecies of copepods were found in the study area: Thermocyclops neglectus decipiens, T. crassu' consimilis, T. incisus, T. inopinus, T. emini, Mesocyclops major, M. ogunnus, M. kieferi and Cryptocyclops linjanticus. More than 60% of all the cyclopoids found were T. n. decipiens and only four species (T. incisus, T. inopinus, T. n. decipiens and M. kieferi) were found infected. Infection rates were very low (< or = 0.3%). The seasonal fluctuations of cyclopoid copepods showed different patterns in the six reservoirs, perhaps related to local circumstances not investigated in the present study. As the people in the study area are very mobile during the dracunculiasis transmission season, it seems likely that some of them become infected at water sources other than the ones investigated. It was therefore difficult to correlate occurrence of cyclopoid copepods in the local water sources with the prevalence of the human infection in the catchment area. No conclusion as to the most important intermediate host(s) in the area could be made.