Evaluation of Subclinical Cutaneous Leishmaniasis Using Leishmanin Skin Test in Keana North-Central Nigeria
L Manu, C Uneke, M Njoku, S Agwale, P Inyama
L Manu, C Uneke, M Njoku, S Agwale, P Inyama. Evaluation of Subclinical Cutaneous Leishmaniasis Using Leishmanin Skin Test in Keana North-Central Nigeria. The Internet Journal of Parasitic Diseases. 2005 Volume 1 Number 1.
Subclinical Cutaneous Leishmaniasis (SCL) was evaluated using the Leishmanin Skin Test (LST) in Keana, North-Central Nigeria. Fifty-three individuals were studied. Fifteen, 28.30% had lesions indicative of previous and active leishmaniasis, 9 (16.98%) had scars while 29(54.72%) had neither scars nor lesions. Lesions and scars were multiple and mostly found on the hind limbs. Mice inoculated with tissue from lesions sampled did not develop lesions. Results showed that 18(34.0%) of the subjects were LST positive with the prevalence higher in the females than the males (42.9% vs 24.0%). The LST positivity occurred with the highest frequency amongst individuals who had scars (44.5%). There was significant difference in the association between sex and the LST positivity (χ 2 = 2.11, df. = 1,
The Leishmania is a group of globally widespread protozoa parasitic organisms, which are causative agents of leishmaniasis.
Different strains cause similar and yet peculiar diseases and symptoms. For instance, cuteneous leishmaniasis of the Old World is called oriental sore and is caused by Leishmania belonging to the
Cuteneous leishmaniasis is on the increase in Nigeria (9, 10). There is need therefore to adopt an easy, rapid, less invasive, specific and sensitive method for mass screening and detection of current and previous infections. This is achieved through immunological techniques, which encompass molecular and cellular biology of antigen recognition and of specific immune reactions and non-specific (1).
The Leishamanin Skin Test (LST) has been used by several researchers (2, 12), and has been reported to measure delayed type hypersensitivity and is being used to assess prevalence of subclinical infections and measures CL transmission rate over time. In this study we used LST to evaluate subclinical cuteneous leishmaniasis in Keana, a known CL endemic area.
Materials and Methods
The study was conducted in Keana, the administrative headquarters of Keana L.G.A of Nassarawa State, North Central Nigeria. Its vegetation is generally Guinea Savannah consisting of tall grasses and patchy trees. The annual rainfall of this zone is about 1500mm and lasts between 6 to 8 months (late March to late October). The weather is relatively hot throughout the year. Sandfly resting sites such as caves, tree holes, cracks in rocks, cavities between boulders, fissures in the ground, buildings, termite hills and animal burrows abound in the area.
The study population comprised of 53 individuals (25 males, 28 males) aged 3 to 60 years. After a successful community mobilization through religious and community leaders in conjunction with the Primary Health Care (PHC) Centre in the locality, the 53 individuals willingly indicated interest to participate in the study. Clinical assessment of subjects was done with respect to the presence of lesions and/or scars and suspected cases were identified by the collaborating PHC Centre. Identification of lesions/scars was done according to the criteria outlined previously (5). However, it was obvious that suspected cases may be having the subclinical leishmaniasis, and that is if other tropical infections with similar manifestations such as tuberculosis and leprosy, are ruled out. Informed consent was duly obtained from each participant, with the assurance that the information obtained would be treated with utmost confidentiality and for the purpose of the research only. Demographic information (age, sex, marital status, occupation, travel history and duration of stay in locality) was obtained from each participant by interview.
The most recent lesions were selected from 3 subjects cleaned with 70% alcohol and small incision was made (through the intact skin to about 2mm deep) at the nodular edge of the sores. Two smears were prepared from slit-skin scrapings of the same lesions, air-dried, fixed with methanol, stained with Giemsa's stain, kept for 20 minutes and washed. Each stain was then screened microscopically for amastigotes. Tissues recovered from skin scraping of the 3 subjects were inoculated into BALB/c mice through the upper footpad. Mice were then observed for the development of lesions as described previously (13, 14).
Leishmanin Skin Test (LST)
The leishmanin antigens used for the skin test were donated by the Laboratory of Leishmaniasis/AIDS Research, University of Jos, Nigeria. The antigens consisted of pooled heat-killed promastigotes derived from
Of the 53 individuals studied, 15 (28.30%) had lesions. Scars were found on 9 (16.98%) of the population; while 29 (54.72%) had no noticeable lesions or scars and hence were considered apparently healthy. Lesions and scars were mostly multiple and present on the legs. Most lesions observed were already resolving and parastiological confirmatory test carried out on a few samples by Giemsa's stain preparation gave no positive result. Mice inoculated with tissue from lesions sampled did not develop lesions. Results from the LST indicated that 18 (34.0%) of the subjects were LST positive. The prevalence was higher among the female than the males (42.9%: 24.0%). The LST positivity occurred with the highest frequency (44.5%) amongst individuals who had scars, compare to the apparently healthy (37.9%) and those with lesions (20.0%) (Table 1).
A number of previous documented investigations of CL in Keana indicated that the area was endemic (10, 13). In this study the cases of lesions (28.30%) and scars (16.98%) which occurred mostly among individuals of age group 11- 20 years confirmed that the infection is still endemic in the area (17). The occurrence of active lesions on legs agrees with the findings of Dedet
The lesions/scars ratio was calculated as an important factor in determining how long disease has been present in the community. However, the ratio does not represent their absolute magnitudes. Factors such as difficulty in finding small leishmanial, scars, women not likely to admit they have scars; and not all inhabitants screened, were possible factors for not calculating the absolute magnitudes (19).
The Leishmanin Skin Test (LST) is still frequently used for clinical diagnosis of the disease and epidemiological surveys on the prevalence of leishmanial infection (1). The prevalence of positive LST of 34.0% observed among the study population in Keana where there is a high risk of infection by
A few samples made by Giemsa's stain preparation did not confirm the disease parasitologically. Mice inoculated with tissues from sampled lesions did not develop lesions. It is reported that in CL, LST would become positive during active phase when lesions are present and may remain positive for life (9, 21). However, many of the individuals with lesions were negative to LST. This could mean that lesions observed may not have been due to leishmaniasis.
This study looked at the possibility of using pooled leishmanin derived from New world and Old world
Reports about cross-reactivity between
This study is not without a few major limitations. Conclusions with respect to age-related susceptibility/exposure could not be properly drawn, largely due to our limited sample size. Strategies should be devised to increase sample size in future studies especially in this part of the globe, where community-based epidemiological studies involving sampling of human population often suffer setbacks because of the unwillingness of many members of the target population to participate. Secondly, our parasitological analysis using the Giemsa staining and the BALB/c mice could not confirm the infection. This may be because the few individuals suspected to have CL from whose lesions, materials were obtained for the parasitological analysis, may not be infected with
Authors wish to thank the traditional ruler of Keana for logistic support in the community mobilization of participants in this study.
C.J. Uneke Department of Medical Microbiology/Parasitology, Faculty of Clinical Medicine, Ebonyi State University, P.M.B 053 Abakaliki, Nigeria Telephone: 234-08038928597 Fax number: 234-04300222 E-mail: email@example.com