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ABSTRACT |
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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40 years), based on the assumption that hydrocele rates may be more prevalent in older age groups. The men were asked if they had scrotal swelling, then examined and tested by the ICT. We found a weakly positive correlation between village prevalence determined by the ICT and hydrocele (r = 0.041, P < 0.001). Only villages with hydrocele rates of 20% or greater were also consistently classified as having endemic filariasis by the ICT. There was no correlation between an individual’s ICT positivity and clinical presence of hydrocele, and questioning about scrotal swelling was not predictive for presence of hydrocele. More research is needed to determine if community level hydrocele prevalence surveys can offer an economical and broadly applicable supplement to the ICT for determining the endemicity of filariasis. |
INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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To determine the target areas for MDA, community serologic surveys are recommended using a rapid immunochromatographic card test (ICT) that qualitatively tests finger prick blood for W. bancrofti circulating Og4C3 antigen.5 The ICT is rapid, highly sensitive and specific, and unlike blood examinations for parasitemia, does not have to take place at night, when the microfilaria of the parasite circulate. In Africa, the two-stage assessment protocol calls for selection of one or two villages in an administrative unit, then ICT testing of a random sample 100 individuals (males and females) in that village. Any positive individual will result in the decision to provide MDA throughout the administrative unit.6 Given the ICT’s expense (costing more than US$1.50 per test), the surveys proposed are limited in their geographic scope. Nigeria, for example, has more than 700 Local Government Areas (LGAs) to be tested, and ICT surveys in just one village per LGA would require well over $100,000 for the purchase of all the required ICT cards.
Hydrocele is the most common clinical manifestation of lymphatic filariasis, and its potential for use as a survey tool has been suggested.7 Up to 40% of men actively or previously infected with W. bancrofti exhibit hydrocele, and in regions of northern Ghana and coastal Kenya endemic for this disease hydrocelectomy accounts for 25% of all surgical procedures.8–10 Hydrocele surveys would be particularly valuable in areas classified as non-endemic by a single village ICT sample where false-negative results lead to a no treatment decision. Such misclassifications might result in entire LGA populations being left out of the MDA program and thus continued transmission of lymphatic filariasis in these regions. If hydrocele surveys had adequate predictive value for lymphatic filariasis (e.g., ICT positivity), they could be conducted more extensively to supplement ICT surveys at a lower cost and in villages where local public health officials believe that this disease is endemic. For these reasons, we undertook a comparative study in Nigeria to evaluate if village hydrocele prevalence could serve as a supplement to the ICT.
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MATERIALS AND METHODS |
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After explaining the purposes of the study to the village chief and traditional leadership council and obtaining their permission, all resident adult males of the village (16 years of age and older) were asked to gather at a central point in the village. The study was explained in Hausa, and those willing to participate were asked to form two lines, one with males 40 years old and another with males < 40 years old. Fifteen males were then randomly selected (every second or third person depending on the number of persons present) from each line, resulting in an overall sample of 30 men of various ages. This method was used to obtain a better distribution of ages to correct for the observation that hydrocele rates increase with age.14
After individual verbal consent was obtained, the patients were assigned an ID number and then taken to a private room or screened examination area and asked in Hausa (which was often translated from Hausa to the local language) their names, ages, occupations, and if they had a swollen scrotum. They were then asked to partially disrobe, and one of two Ministry of Health nurses (IG or JU) trained to differentiate hydrocele from inguinal hernia performed a physical examination focused on the scrotum and inguinal area. Clinical hydrocele (referred to herein as hydrocele) was diagnosed based on the finding of a nontender, soft, fluid-filled mass whose superior limit could be defined the examining finger. Transillumination was difficult due to heavy scrotal pigmentation and lighting conditions and was not included as a criteria. Clinical hydrocele was distinguished from indirect inguinal hernia (which would change with cough or straining, show an inguinal swelling at the internal ring, and whose superior limit of mass in scrotum not defined with the examining finger), epididymitis (tenderness), tumor (painless, hard and irregular), scrotal lymphedema (internal scrotal contents normal on palpation), and inguinal adenopathy (hanging groin). In the initial village examinations, a physician (FOR or ESM) was present to verify that the nurses were capable of an accurate clinical distinction of hydrocele from these other entities. If a hydrocele was present, its size was determined (in the event of bilateral hydrocele, the largest hydrocele was measured and recorded). Initially, the physicians and nurses attempted to measure the circumference of the hydrocele using a disposable tape measure, but this proved difficult and poorly reproducible. After the first 50 villages, the procedure was altered and examiners were asked to subjectively equate hydrocele size (volume) to the sizes of three fruits kept by the team during the surveys (an orange, coconut, and papaya). The sizes were then converted to a standard centimeter circumference at the time of data entry. Data were not recorded on presence of inguinal hernia or surgical scars.
Immediately after the physical examination, ICT testing was performed following kit instructions (ICT Diagnostics, Balgowlah, Australia, product number FLO.1; patent now sold and produced as NOW®, ICT filariasis kits; Binax, Portland, ME). The patient’s left index finger was cleaned with 70% isopropanol and then punctured using a sterile lancet. The initial sample of blood was removed using a cotton swab, and sufficient fresh blood was then obtained to fill a 100-µl capillary tube. The blood was then transferred from the capillary tube to the pad on the ICT test kit card; two drops of the accompanying reagent were then added to the pad and the card was sealed. The results of each ICT test card were read after 15 minutes. A positive result was when two pink lines appeared on the card’s window, and a negative result was when a single line was seen. Test results with the individual’s ID number were recorded both on the card, and on each individual’s data sheet. Village summary data sheets were prepared at the end of each visit on which the 30 ID numbers and their corresponding ICT results (positive/negative) and hydrocele results (positive/negative) were recorded.
Data were entered into a computer and statistical analysis was carried out in Epi Info 6.04d (Centers for Disease Control and Prevention, Atlanta, GA) and SAS version 8.0 (SAS Institute, Inc., Cary, NC) software packages. Correlation analyses were carried out for ICT and hydrocele results at both the individual and village levels (e.g., village ICT prevalence compared with village hydrocele prevalence). Villages were considered to have endemic filariasis if at least one individual from the village sample had a positive ICT test result for filarial antigen. Individual analysis also included evaluating the relationships between age, history of scrotal swelling, ICT, hydrocele presence, and size of hydrocele. Chi-square tests were used to compare dichotomous variables; continuous variables were compared using the Kruskal-Wallis (non-parametric) test.
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RESULTS |
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Individual analysis.
Most participants (81.6%) were agricultural workers and had resided their entire lives in the village. Self reported ages ranged from 16 to 101 years, with many of the older men not knowing their year of birth; the median age was 35 years. Hydroceles were diagnosed in 531 individuals (12.9%). Hydrocele prevalence increased with age, being present in more than 20% of men reporting their ages to be 50 and older (Figure 1
). The median age of patients with hydrocele was 50 years old (range = 20–90 years old), which was significantly older from that of those without clinical hydrocele (P < 0.0001, by Kruskal-Wallis test). Only 68% of the individuals found to have hydrocele by examination reported having scrotal swelling on the history taken prior to the examination; those with larger hydrocele were more likely to report its presence (P < 0.01, by Kruskal-Wallis test). The mean hydrocele circumference size was 26 cm (range = 10–85 cm).
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), and in the youngest age groups ICT positivity was four times greater than the corresponding hydrocele rate. However, men with hydrocele were no more likely to be ICT positive than men without hydrocele; 28% of men with hydrocele were ICT positive, compared with 22% of those without hydrocele (odds ratio = 1.22, 95% confidence interval = 0.98, 1.52).
Village analysis.
The mean village hydrocele prevalence was 12.2% (range = 0–43.3%), compared with a mean village ICT prevalence of 22.6% (range = 0–66.7%). The ICT rates compared with hydrocele rates fluctuated widely, although the correlation analysis showed a positive statistical association between village hydrocele prevalence and ICT prevalence (r = 0.41, P < 0.001; Figure 2). Hydrocele rates 20% (six or more men with hydrocele in the 30-male sample) only occurred in villages where there were also one or more individuals with positive ICT results. Thirty-six villages (25%) of the 144 in the study had such high hydrocele rates. The 11 villages (7.6%) whose samples were entirely ICT negative occurred exclusively among those villages with hydrocele rates less than 20% (
2 = 4, P = 0.046). However, among the 18 villages (13%) that had hydrocele rates of 0, only three had negative ICT results (mean ICT positivity = 13.7%, range = 0–43%).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
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It is possible that the many years of mass treatment with ivermectin (for onchocerciasis) in these LGAs influenced the results obtained. This consideration would assume a disparate impact of ivermectin treatment on filarial hydrocele prevalence (an irreversible condition unchanged by ivermectin treatment) compared with ICT prevalence rates (possibly reduced by treatment). We do not believe this to be the case. First, if ivermectin treatment had the proposed effect, we would expect more ICT-negative villages. In fact, only 8% of villages had ICT negative samples, compared with 21% of villages with ICT rates greater than 40%. Second, Eberhard and others found that Og4C3 antigen levels (e.g., ICT positivity) do not decrease with ivermectin treatment in the same manner as does microfilaremia prevalence and intensity, perhaps due to the fact that ivermectin does not kill the adult W. bancrofti worms (and ICT detects circulating antigen from both microfilaria and adult worms).15 The impact of ivermectin treatment activities on mapping of lymphatic filariasis is an important one for Nigeria, since more than 16,500,000 treatments were provided in Nigeria in 2001 (Nigeria National Onchocerciasis Task Force, Federal Ministry of Health, unpublished data). Thus, future ICT surveys proposed for the lymphatic filariasis program in Nigeria, similar to the ones in this study, will often occur in areas already exposed to MDA. It would appear from our results that ICT results in lymphatic filariasis mapping activities will not be influenced by the ongoing onchocerciasis ivermectin treatment program.
This study sought to identify hydrocele, which was a clinical diagnosis based on the finding of a discrete, nontender, fluctuant mass around the testes that was not explained by indirect inguinal hernia or scrotal lymphedema. In our experience, nurses were as capable as physicians in not confusing these and other conditions (such as inguinal adenopathy, hanging groin, and acute epididymitis) with hydrocele. However, malignancy, varicocele, chylocele, spermatocele/cyst, or chronic epididymitis could have been recorded as hydrocele in our study, and some hydrocele could have been other than filarial in etiology (e.g., traumatic, tuberculous, idiopathic, etc.).
We recommend that if hydrocele surveys are used, they be based on actual physical examinations and not questionnaires, since we found that 32% of the men with physical finding of hydrocele did not report scrotal swelling when asked. In addition, questionnaire surveys for hydrocele would also fail to distinguish hydrocele from other easily differentiable causes of scrotal swelling. Physical examinations could be carried out by personnel trained to correctly distinguish hydrocele from other forms of scrotal pathology. Careful study is required to determine the best way to effectively provide such training.
Patients with clinical disease from lymphatic filariasis are often antigen or microfilaria negative. In a review of 23 published studies, Michael and others found similar rates of disease in both microfilaremic and amicrofilaremic persons.16 A report by Addiss and others found that 35% of 57 Haitian men with hydrocele were Og4C3 antigen negative.17 Consistent with these reports, we also found individuals with clinical hydrocele to be no more likely to have positive filarial antigen test results than men without hydrocele. However, this finding was initially quite confusing to the field staff, who expected that the ICT test results should be positive in hydrocele patients (e.g., as a diagnostic test for lymphatic filariasis). Staff confusion was abated by explaining to them that lymphatic filariasis often occurs after the body has mounted an effective immune reaction; that is, manifestations are residual effects of past filarial infection, e.g., burnt-out disease. Thus, persons with hydrocele and other manifestations of lymphatic filariasis may no longer have living worms, or circulating worm antigens, in their bodies to give a positive reaction on the ICT test. Nurses and physicians were satisfied by this explanation.
In conclusion, we found that only a very high village prevalence of hydrocele consistently identified the coexisting prevalence of lymphatic filariasis antigenemia (as measured by ICT positivity) in central Nigeria. We recommend further research to determine if and how hydrocele surveys can be used in lymphatic filariasis elimination programs as a supplement or alternative to ICT mapping for targeting mass treatment programs.
Acknowledgments: We thank the following individuals for their help: B. Bagnall, R. Barwick, I. Dhillon, M. Iwamoto, J. Jiya, C. MacKenzie, J. Roberts, and A. Hightower. The Carter Center assisted the Ministry of Health Program for Onchocerciasis in Plateau and Nasarawa States, and is in partnership with the Lions Club’s SightFirst Program and the African Program for Onchocerciasis Control. We also thank L. Rakers for providing invaluable help in manuscript preparation and editing.
Financial support: Activities in this project were carried out with grant support from GlaxoSmithKline.
Authors’ addresses: Abel Eigege, Frank O. Richards Jr., Emmanuel S. Miri, John Umaru, Wanjira Mathai, Stanley Amadiegwu, and Donald R. Hopkins, River Blindness Program, The Carter Center, One Copenhill, Atlanta, GA 30307, Telephone: 770-488-4511, Fax: 770-488-4521, E-mail: sdsulli{at}emory.edu. David D. Blaney, Rollins School of Public Health, Emory University, Grace Crum Rollins Building, 1518 Clifton Road NE, Atlanta, GA 30322. Ibrahim Gontor, Plateau State Ministry of Health, State Secretariat, Jos, Nigeria. Gladys Ogah, Nasarawa State Ministry of Health, State Secretariat, Lafia, Nigeria. M. Y. Jinadu, Room 913, Phase II, Federal Secretariat, Lagos, Nigeria.
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REFERENCES |
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  E. Mathieu, J. Amann, A. Eigege, F. Richards, and Y. Sodahlon Collecting Baseline Information for National Morbidity Alleviation Programs: Different Methods to Estimate Lymphatic Filariasis Morbidity Prevalence Am J Trop Med Hyg, January 1, 2008; 78(1): 153 - 158. [Abstract] [Full Text] [PDF]
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 J. Iqbal and A. Sher Determination of the prevalence of lymphatic filariasis among migrant workers in Kuwait by detecting circulating filarial antigen. J. Med. Microbiol., April 1, 2006; 55(Pt 4): 401 - 405. [Abstract] [Full Text] [PDF]
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| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
