|DAVID AJIBOYE OJO|
|Department Of Biological Sciences, University o Agriculture, Abeokuta.|
|Investigations were conducted on aspects of the epidemiology of malaria and typhoid
infections in Abeokuta, the capital city of Ogun state located in the forest zone of southwest Nigeria.
Using cross-sectional and longitudinal studies, blood samples were examined in children <15 years, for malaria parasitaemia, Widal serologic reactions and other haematological parameters (PCV, fib, ABO system, Rh factor and Fib genotype). Seasonal variations in malaria, typhoid infection and fever as well as in mosquito abundance were investigated. Structured questionnaires were used to obtain information on the knowledge, attitudes, beliefs and practices of the residents and medical personnel with respect to malaria infection.
The overall prevalence of infection was 59.9% (Plasmodium falciparum accounted for 89.7% and Plasmodium malariae 10.3%), and females were significantly more infected (64.3%) than males (56.1%) (P = 0.05); so also more children aged 0 - 5 years were infected (83.1 %) than other age groups. More children were infected in the high density areas (64.3%) than low density areas (46.4%) (P = 0.235). There were significant differences in malaria infection among the various Hb genotypes (P < 0.0001). Also malaria was significantly higher among children with severe anaemia (1' < 0.0001). However there was no significant difference between malaria infection among the different blood groups (P = 0.357) and in the Rhesus antigen (P = 0.4390) nor was there difference between the nutritional status of infected and non-infected children (P = 0.8273). Gametocytopaenia was 7.9% and was significantly higher among the youngest age group (P < 0.0001). Parasite density increased with increasing body temperature (P < 0.0001).
The prevalence of typhoid infection was 17.4% but did not differ between sexes (P = 0.8522) although significantly higher among older children (P = 0.0001). Among 500 blood and stool samples respectively screened for Widal agglutination reaction and stool cultures, growth was recorded in 54.5% and 100% of samples with titre values 1:160 and 1:320 respectively.
Observations from the longitudinal study carried out between October 2000 and September 2001, showed that of the 3997 feverish cases recorded, 82.4% and 32.8%. were respectively due to malaria and typhoid. Fever and malaria were significantly higher in the wet than the dry season (P < 0.0001). Fever significantly correlated with malaria all year round (P = 0.0005) but only correlated with typhoid in the dry season (P = 0.0370). Linear regression models showed that fever appeared to predict malaria infections (t = 30.838, P = 0.0005) better than typhoid infection, (t = 1.322, P = 0.2160).
Of the 3290 mosquito caught by human bait between September 2001 and August 2002, 48% were Anopheles species, while 88% of the Anop heles species was An.
gambiae. This species is considered the main vector in the study area. Mosquito
abundance was significantly higher in the wet than dry season (P < 0.0001), while the mean biting density was higher in the high density than low density areas of the city (P < 0.0001). Also mosquito abundance significantly correlated with rainfall (P 0.002) and relative humidity (P = 0.01) but not with temperature (P = 0.745).
Most households in the high density areas have a mean greater than 10 occupants per house, but below 10 occupants in the low density areas. Most of the residents (> 90%) were knowledgeable about mosquito breeding and the association between it and malaria. The use of door and window nettings against mosquitoes, were common
practices in the low density areas and almost absent in the high density; preferring
mosquito coils-and insecticides.
Sixty percent of attendance at clinics/hospitals were due to malaria, with fever, headache, body pain and vomiting being the main symptoms. The first line drug is chloroquine but they reckon that at least 30% of cases present malaria resistant to chloroquine; to which alternative drugs such as fansidar (pyrirnethane + sulfaloxine), halfan (halofanthrine hydrochloride) and quinine arc administered. Drug abuse, incomplete dosage and adulterated drugs were considered as the most important causes of resistance. The large number of patent medicine stores in the city whose source of drugs are questionable is thought to be a source of concern.
A large number of residents in the high density areas use local herbs as alternative treatments for fevers of different origin. These herbal treatments were usually decoctions of roots, leaves and barks extracts in aqueous or alcohol. A wide variety of plant species used are documented, and include Citrus medica (Ijagain), Enantia chlorantha (Awopa), Azadiraeta indica (Dogoyaro), Khaya senegalensis (Oganwo), Alstonia boonei (Epo ahun), Mangifera indices (Mango), Morinda lucida (Oruwo), Pentachlethra macrophyla (Aidan), Carica papaya (Ewe ibex), Jatropha caucus (Botuje), Manihot species (Ewe paki), Citrus species (Osan wewe), Anacaudium occidentals (Cashew), Piper guineensis (lyere) and Phumbago zeylanica (Inabiri).