Human onchocerciasis: current assessment of the disease burden in Nigeria by rapid epidemiological mapping.

Rapid epidemiological mapping of onchocerciasis (REMO) was carried out in Nigeria between 1994 and 1996, to provide accurate estimates of the populations living in high-risk areas for the disease and to identify the communities to be given priority treatment with Mectizan (ivermectin, MSD). The rapid epidemiological assessment (REA) teams which carried out the survey comprised epidemiologists, geographers, and entomologists. They used topographical maps, at a scale of 1:250,000, to select sample villages at 30-km intervals along selected river courses. Several non-governmental development organizations participated in the surveys, providing support to the teams. In each study community, 50 adult males who had lived in the area for at least 10 years were randomly selected and examined for the presence of palpable, onchocercal nodules. The REA results were cross-validated by an independent REMO expert and then presented, initially as percentage prevalences in pie-chart form, using a geographical information system. The number of Nigerians living in high-risk areas (demarcated by river systems with villages that had > or = 19% prevalence) and who therefore require urgent Mectizan treatment, was estimated as 13,809,313. The national REMO map produced is allowing the African Programme for Onchocerciasis Control's technical consultative committee to prioritize the approval of proposals submitted from Nigeria in a rational and effective manner.

Severe morbidity among children in a trial malaria chemoprophylaxis with pyrimethamine or chloroquine in Ibarapa, Nigeria.

In a controlled trial of weekly malaria chemoprophylaxis with chloroquine and pyrimethamine there were no significant differences in type and frequency of severe morbidity during chemoprophylaxis. Administration of chemoprophylaxis during the current and immediately preceding month was associated with significantly fewer episodes of severe morbidity in the chloroquine and pyrimethamine groups when each was compared with the control multivite group. After chemoprophylaxis had been stopped, significantly more episodes of severe morbidity occurred in the chloroquine group than the control group, but a similar trend in the pyrimethamine group was not statistically significant. In the control group most of the episodes of severe morbidity, including those episodes which were associated with heavy parasitaemia, occurred below the age of 4 years. In contrast, the children who received chemoprophylaxis continued to experience such illness at older ages. The difference between the chloroquine group and the control group in respect of age at time of severe morbidity was statistically significant.

Preliminary observations on the distribution of ivermectin in Nigeria for control of river blindness.

A total of 118,925 individuals in four Nigerian states was treated for onchocerciasis between February and December, 1991, using centralized and house-to-house distribution of ivermectin. Pre-treatment prevalences of the disease ranged between 28% and 90%. Only 0.7% of those treated reported adverse reactions within three days of treatment: 230 individuals (0.19%) had headache, 210 (0.17%) general body pains, 150 (0.12%) pruritus, 120 (0.10%) oedema, 80 (0.06%) fever, 20 (0.02%) dizziness, 15 (0.01%) vomiting, 10 (0.01%) diarrhoea, and 25 individuals (0.02%) noticed that they passed intestinal worms. Treatment in the endemic communities continues. The results show that mass treatment of onchocerciasis with ivermectin is quite safe and the drug's acceptability increases its potential as the drug of choice for control of onchocerciasis in Nigeria.

Synergistic effect of migrating Ascaris larvae and Escherichia coli in piglets.

The effect of intestinal flora on the establishment, development and pathogenicity of Ascaris suum larvae in piglets (Large White breed) was investigated. The infected piglets with Ascaris and Escherichia coli showed signs of pneumonia, cough with respiratory difficulties initially even though these moderated with time. They lost appetite and showed signs of unthriftiness with loss of weight. The packed cell volume was normal but the differential leucocyte counts of the pigs infected with Ascaris larvae and bacteria had high neutrophils, unlike the very high lymphocyte count observed in piglets with ascarids only. The piglets had generalized serous atrophy of body fat. The pericardial and perirenal fats were gelatinous. There was a firm and nodular grey and red hepatization with abscess pockets in the intermediate and anterior one third of the diaphragmatic lobes of the lungs. The liver contained greyish-white and depressed focus immediately dorsal to the area of attachment to the gall bladder with multifocal areas. There was no significant gross lesion in the control animals. Cultural and microscopic examinations of some internal organs of the infected animals showed that bacteria were carried to the lungs by the migrating Ascaris larvae. The combined synergistic effect of Ascaris larvae and E. coli was also investigated and it was concluded that the two agents (A. suum larvae and E. coli) worked together synergistically.

Morphology and identification of Chrysops larvae from Nigeria.

Mature larvae of four Afrotropical species of Chrysops (Diptera: Tabanidae): C. centurionis Austen, C. distinctipennis Austen, C. longicornis Macquart and C. silaceus Austen, are described and illustrated from specimens collected in Nigeria, identified by rearing associated adult flies. The descriptions pay special attention to the value of ultrastructural characters, such as cuticular striations, observed by scanning electron microscopy (SEM).

Specific serodiagnosis with adult Onchocerca volvulus antigen in an enzyme-linked immunosorbent assay.

The cross-reactivity of the blood from onchocerciasis, loiasis, and dipetalonemiasis was tested by a micro-ELISA technique, utilizing adult Onchocerca volvulus antigen and blood samples taken on filter paper. The average ELISA values (OD at 500 nm) were as follows: 0.58 in persons with O. volvulus microfilariae (n = 81), 0.49 in microfilariae-negatives from the same endemic area (n = 39), 0.15 in dipetalonemiasis (n = 27), and 0.25 in loiasis (n = 12), while those of 65 Dipetalonema perstans-negative people were markedly low (average 0.14) and that of 22 Loa loa-negatives, 0.22, respectively. This ELISA could successfully differentiate onchocerciasis from dipetalonemiasis and loiasis.

Ascaris lumbricoides as a vehicle of bacterial infections.

Investigations were conducted on microflora on the body surface and internal organs of adult Ascaris lumbricoides. The investigations involved examination of wet faecal preparations of over 100 pupils using light microscope. The body surface of the adult Ascaris worms was cultured on selective media. Adult worms were dissected and different parts of the worms' gut were cultured for isolation of micro-organisms. The results of the bacteriological examination of the body surface of A. lumbricoides yielded many genera of bacterial organisms. The results from internal organs of dissected adult Ascaris worm yielded varying percentages of organisms similar to those found on the surface of the worm. The possibility of linking Ascaris infection with this aetiology of pyrexia of unknown origins as commonly seen in tropical regions was discussed.

Infectivity with human ascariasis in Ibadan Oyo State, Nigeria.

Some of the common foodstuffs that assist in the transmission of ascariasis in Ibadan have been determined. The frequency of recovery of Ascaris ova in the different food samples examined varied from 9.6% in tomatoes to 25.6% in lettuce leaves. The indiscriminate pollution of Ibadan environment with human faeces enables the foodstuff consumed raw to serve as effective sources of heavy Ascaris infection which lead to other medical complications. The strategies for the control of Ascaris infection in Ibadan were discussed.

Schistosomiasis: assessment of the sensitivity, specificity and reproducibility of serological methods for the diagnosis of schistosomiasis in Nigeria.

Three groups of sera were tested by indirect fluorescent antibody (IFA), complement fixation (CF) and counter-current immunoelectrophoresis (CCIE) techniques; 56 (10.1%) of 554 sera from Nigerians were anticomplementary and so could not be tested by the CF. Crude antigen extract of adult Schistosoma mansoni was used in the CF and CCIE tests and cercarial antigen in the IFA test. IFA was the most sensitive test and CF the most specific. The reproducibility of both these tests was good. The CCIE was the least sensitive and specific, and its reproducibility was poor. The IFA test was the most suitable for Nigerian conditions. Cross-reactions to S. haematobium antibodies were consistently present in all three tests and it was not possible to differentiate serologically S. mansoni from S. haemotobium. The interpretations of the results presented some difficulties because of the frequency of cross-reactions and false-positives, but the data fell within the infection prevalence rate of 50% reported earlier from south-western Nigeria. The IFA test was more specific and is considered ideal for serodiagnosis.

Maxillary African histoplasmosis mimicking malignant jaw tumour.

An account is given of an unusual presentation of solitary Histoplasmosis duboisii of the jaw simulating a malignant neoplasm. This report is of interest for two reasons; firstly, the rarity of such a presentation and secondly, the extensive search of the literature which has failed to produce another case. The rationale for our treatment is also briefly discussed.

The application and limitations of immunodiagnostic techniques in parasitic infections.

The application of immunodiagnostic techniques in the diagnosis of parasitic infections has been discussed in relation to the conditions operating in developing countries where multiple parasitism is common and diagnostic facilities are often limited. The uses and limitations of the tests for individual diagnosis and epidemiological studies have been highlighted. The filter-paper plasma modification of the IFA test has been identified as a technique that has an advantage over all the others and could be universally used with great success in many developing countries.

The prevalence of human intestinal protozoa in Ibadan, Nigeria.

This study shows that the two intestinal protozoa, Giardia lamblia, Balantidium coli in addition to Entamoeba histolytica are prevalent in the Ibadan population and are responsible for many of the non-bacterial diarrhoea seen in patients. A high seasonal prevalence of the intestinal protozoa in the dry months of the year was associated with the use of contaminated water. Both the high infection rates recorded in adults and children under five years old, and the high frequency of association involving Trichomonas hominis, Entamoeba histolytica and Giardia lamblia were discussed.

Loa-loa microfilaremia in the Nigerian population.

In about half of 1026 Nigerians infected with Loa loa, the microfilaria levels were low, less than 8% had more than 1000 microfilariae in 50 cumm blood. The length range of 445 microfilariae obtained from 39 infected people was 156.8 to 308.7 micron with a mean of 236.4 micron, or microgram; smaller than in the Kumba strain of Cameroon. The persistence of a rather high number of microfilariae in the peripheral blood of four patients till 22 hours was discussed in relation to the importance of Mansonia africana mosquitoes as a vector of Loa loa.