The rapid monitoring of ivermectin treatment: will school-based surveys provide the answer?

The data on ivermectin-treatment coverage recorded in household surveys sometimes conflict with those recorded in school-based surveys or in the relevant treatment registers maintained by community-directed distributors (CDD). An attempt has now been made, in two sites in Nigeria (Enugu and Kaduna states) and one in Sudan (Abu Hamad province), to determine how well these three sets of data are correlated (and to explore the effectiveness of several alternative channels for the delivery of treatment-monitoring forms to schools). Using a cross-sectional approach, data were collected from primary schools, households and treatment registers. Calculation of Pearson's correlation coefficients (r) indicated that, overall, the data from the household surveys were very similar to those collected using the school-based strategy (r=0.66; P<0.0001) or from the treatment registers of the CDD (r=0.86; P<0.0001). The information recorded in the CDD registers also closely matched that recorded in the school-based surveys (r=0.67; P<0.0001). These encouraging results for the pooled data masked some inter-site differences. The correlation between the household-survey and treatment-register data was, for example, only good in Enugu (r=0.89; P<0.001), and was too weak to be statistically significant in Abu Hamad or Kaduna. Although the results of the school-based survey in Kaduna also did not closely correlate with those of the corresponding household survey (r=0.10; P=0.71), the household survey at this site was probably not conducted as well as those at the two other sites. In general, it appears that school-based surveys are an effective means of monitoring community coverage with ivermectin, rapidly, accurately and at relatively low cost. It is therefore recommended that school-based methods of monitoring of coverage are adopted by programme managers.

Review of the publications of the Nigeria national blindness survey: methodology, prevalence, causes of blindness and visual impairment and outcome of cataract surgery

This is a review of the major publications from the Nigeria national blindness survey in order to highlight major findings and challenges of eye care in Nigeria. The review summarizes methodology and key findings. Survey publications on methodology, prevalence and causes of visual impairment and outcome of cataract surgery were retrieved, reviewed and relevant data extracted, reported and discussed. The study was the largest and more detailed eye survey in Nigeria (15,375 people 40 years and older recruited). Participants had detailed eye examination including visual acuity, autorefractokeratometry, A- scan biometry, visual field and basic eye examination. Cause(s) of visual impairment in each eye using WHO algorithm was determined among participants with vision < 6/12. Some of the participants also had qualitative questions on barriers to uptake of services, quality of life and visual function. Major highlights of the results as contained in the publications include a high prevalence of blindness with 4.2% (95% CI: 3.8-4.6%;),of the study population having blindness (using presenting vision (PVA)) even with best correction the prevalence was 3.4% (95% CI: 3.0-3.8%. The prevalence of SVI using PVA was 1.5% (95% CI: 1.3-1.7%).and with best correction 0.8% (95% CI: 0.7-1.0%). Blindness varied by age groups, sex, literacy level and geopolitical zone. Furthermore, 84% of blindness was due to avoidable causes with cataract responsible for 43% of blindness, glaucoma 16.7%, uncorrected aphakia 8.4% and corneal opacity 7.9%. Of the total 538 eyes that had cataract surgery procedures, 42.7% had couching and the remaining had cataract surgery, but only 41.4% of cataract operated eyes had IOL surgery. Outcome of cataract surgery was good at presentation for only 30.8% of eyes (84 eyes) which improved to 56.8% with correction. The possible remedy for the high burden of needless blindness and harmful eye health practices in Nigeria are discussed.

The Problem of Trachoma within an Onchocerciasis-Endemic Zone in Kaduna: Need for a Multilateral Approach?

INTRODUCTION

Within the mesoendemic onchocerciasis belt of Kaduna State, Northern Nigeria, there were other causes of ocular morbidity as well. We investigated the contribution of trachoma.

METHODS

A total of 6831 individuals were examined for eye disease, including signs of trachoma.

RESULTS

The overall prevalence of trachoma was 4.5% (577 eyes of 310 individuals), making it the second most common cause (1 in 5) of ocular morbidity after cataracts. Of the 577 eyes, 405 (70.2%) had cicatrizing disease while the rest had active disease. Overall, the prevalence of TF was 1.1% (1.3% in those < 10 years of age), TI 0.2%, TS 3%, CO 0.5% and TT 1.1% (4.3% and 3.5% in subjects aged > 55 and > 40 years, respectively). The prevalence of trachoma increased with age. The overall prevalence of blindness in the whole population was 2.7%. Trachoma accounted for 11% of this. On the other hand, onchocerciasis accounted for 3.1% of the overall ocular morbidity (less than trachoma) and 39% of the blindness.

CONCLUSIONS

There appears to be a clear need to retrain middle cadre ivermectin workers in trachoma rapid assessment and SAFE strategy intervention methods in order to further impact blindness prevention in these 'onchocerciasis-endemic' zones.

Blindness: how to assess numbers and causes?

BACKGROUND

Traditionally, blindness surveys have modelled themselves on the "gold standard" of a census and examination of a whole population. Blindness, however, is a relatively rare condition even in badly affected communities; hence, large sample sizes are required to gain adequate estimates of prevalence, particularly by cause.

METHODS

Three assessments of blindness prevalence and aetiology in the same communities are reported. One involved asking individuals questions concerning their visual status during a census (perceived visual status, PVD), one involved examination of all ostensibly visually disabled people presenting to a central point within each community (examination of the visually disabled, EVD), and the final assessment involved a gold standard examination of the whole population (whole community examination, WCE).

RESULTS

In a population of 8139 the blindness prevalence was 2.7% PVS, 3.6% EVD, and 3.1% WCE. Attributed causes of blindness were not representative in the PVS except for cataract. The END yielded cause specific estimates not far from those found at WE except for a relative under-representation of glaucoma and optic atrophy.

CONCLUSION

Since cataract is, by a significant margin, the most common cause of blindness in the world such a simple method as asking individuals if they are blind and what they believe to be the cause may yield adequate estimates of the problem for planning eye care strategies for this condition. Alternatively, an ophthalmologist visiting villages and examining allcomers for visual disability may provide reasonably accurate cause specific prevalence estimates without the expense of a major blindness survey.

Glaucoma prevalence may not be uniformly high in all 'black' populations

Epidemiological data on the prevalence of glaucoma are generally presented for populations described as "whites" or "blacks". "Black" populations appear to have a higher glaucoma preva lence than "white" populations. We describe a population-baseed survey for glaucoma in rural Northern Nigeria. A total of 1563 Hausa/Fulani individuals aged 5 years and above, underwent an extensive screening test and a detailed ophthalmological examination was performed on individuals who failed the test. The overall prevalence of open angle glaucoma in this population was 1.02% (0.12 to 3.64, 95% confidence interval) in individuals 45 years of age and older. This is lower than the prevalence rates reported for other "black" populations. The low prevalence of glaucoma detected in this African population may be, to some extent, a reflection of the age structure of the population studied or methodological differences in ophthalmic examinations performed. It is also possible that the prevalence of glaucoma varies considerably between "black" populations due to genetic heterogeneity or the effect of some unidentified environmental exposure. The use of the simple description of populations as 'black' (or 'white'), which focuses on a commonality, tends to obscure the potential heterogeneity within and between populations and thus may be unhelpful in some circumstances.

Intraocular pressure and gonioscopic findings in rural communities mesoendemic and nonendemic for onchoceriasis, Kaduna State, Nigeria

PURPOSE

To report on glaucoma-related ocular parameters, namely intraocular pressure and peripheral anterior synechiae, in the presence of onchocercal infection.

METHODS

Two computer-generated random samples of individuals were drawn from communities mesoendemic and nonendemic for onchocerciasis respectively. Applanation tonometry and gonioscopy were carried out on these individuals.

RESULTS

Four hundred and thirty-six and 319 individuals from the mesoendemic and nonendemic communities were examined respectively. The mean intraocular pressure was 1.58 mmHg lower in the individuals from the mesoendemic communities compared with those from the nonendemic communities (p < 0.001) despite the prevalence of peripheral anterior synechiae being higher in the mesoendemic communities. In these communities, there was strong evidence that the prevalence of peripheral anterior synechiae increased with increasing microfilarial load.

CONCLUSIONS

Onchocercal infection produces a low-grade inflammatory process, which may result in a lowering of intraocular pressure despite the formation of peripheral anterior synechiae. Glaucomatous optic nerve damage may therefore not be the primary cause of visual loss in ocular onchocerciasis as this occurs late and is probably preceded by other blinding onchocercal pathology.

Ambulatory blood pressure monitoring: technique and application in the study of cardiac dysfunction and congestive heart failure

Ambulatory blood pressure monitoring has become a widely used method of blood pressure and heart rate evaluation in the free-living subject. Recently, ambulatory monitoring has become covered by Medicare for the evaluation of "white-coat" hypertension. Although the technique provides only intermittent readings throughout the 24-hour period, average blood pressures obtained in this way correlate well with a variety of hypertensive disease processes and are also a better prognostic marker for future cardiovascular events than office blood pressure. Ambulatory blood pressure averages also correlate well with indices of diastolic dysfunction. In patients with congestive cardiac failure and systolic dysfunction, ambulatory monitoring suggests an impaired circadian blood pressure profile with high nocturnal blood pressure. Further research is needed on the relationship between ambulatory blood pressure and cardiac dysfunction, as well as the impact of observed circadian blood pressure changes on outcome. (c)2001 CHF, Inc.

Trial of Trachoma Rapid Assessment in a subdistrict of northern Nigeria

PURPOSE

To assess the usefulness of Trachoma Rapid Assessment (RA) in priority ranking of trachoma areas.

METHODS

RA was conducted concurrently with a cross-sectional trachoma prevalence survey in some villages selected from the communities at risk for trachoma in the Kaita Local Government Area of northern Nigeria. The RA team consisted of two ophthalmic nurses. Pen torches and loupes were used for the examination. Data were collected on the seven components of the RA 'information pyramid' for all the selected villages. The data were analyzed using the RA methodology guidelines to determine the priority villages for trachoma intervention. This was compared with the ranking from the cross-sectional trachoma prevalence survey.

RESULTS

The results of RA were found to be in agreement with the cross-sectional survey in 53.3% of the villages in the priority ranking of trichiasis, while in the priority ranking of active trachoma the agreement between the two methods was found to be 60%. The risk factors for trachoma were shown to be of high magnitude in all the villages using both the RA method and the prevalence survey.

CONCLUSION

RA may be a more useful tool when applied to a vast area where the risk of trachoma is likely to differ greatly between different parts of the area. In the determination of the trichiasis pattern of a community by RA, it may be more useful to use the actual number of trichiasis cases in the area rather than the prevalence of trichiasis. The operational definition of some risk factor indicators seems very subjective and vague. The RA method needs more validation to sharpen the indicators used.

Magnitude of trachoma and barriers to uptake of lid surgery in a rural community of northern Nigeria

AIMS

A population-based cross-sectional survey for trachoma prevalence was conducted in a subdistrict of northern Nigeria. The objectives of the survey were to determine the magnitude and pattern of trachoma and the barriers to uptake of lid surgery in the area.

METHODS

A total of 2903 people of all ages were examined out of 3715 registered eligible persons. The study population was chosen by a two-stage cluster random sampling technique. Each person was examined for signs of trachoma. The World Health Organization (WHO) simplified trachoma grading was used. Persons with trichiasis that had not attended hospital were asked why they had not sought hospital treatment.

RESULTS

A blindness prevalence of 1.5% (95% CI 0.4%-2.7%) was found in the study population. About 20% of the blindness were due to trachoma. The prevalence of trichiasis among women 15 years and above was found to be 8.6% (95% CI 6.8%-10.7%). The prevalence of active trachoma among children was 11.8% (95% CI 10.1%-13.3%). Over 90% of people with trichiasis have not sought medical attention. The major identified factor that prevents people from accessing hospital treatment for trichiasis was cost (57%).

CONCLUSION

This study suggests that trachoma is of public health significance in this area; as such, an effective trachoma control program with emphasis on lid surgery should be established.

Audit of outcome of an extracapsular cataract extraction and posterior chamber intraocular lens training course

BACKGROUND

A training course for cataract surgery with intraocular lens implantation was organised in April 1997 at the National Eye Centre, Kaduna, Nigeria. Operations were performed by six Nigerian consultant ophthalmologists under the supervision of two surgeons from Aravind Eye Hospital, India.

METHODS

A total of 175 eyes with uncomplicated cataracts were operated on after careful selection. All but six patients had extracapsular cataract extraction with posterior chamber intraocular lens insertion during the training programme.

RESULTS

The mean age of the patients at operation was 54. 2 years. One hundred and forty five of the operated eyes (85.8%) were blind before surgery of which six (3.6%) remained blind postoperatively. An uncorrected visual acuity of 6/60 or better was achieved in 87.3% eyes after surgery. Forty one patients (24.3%) were blind before surgery, two of whom (1.2%) remained blind afterwards. The most common intraoperative complication was posterior capsular rent which occurred in 10 eyes (5.7%); striate keratopathy/corneal oedema and cortical remnant were the most common immediate postoperative complications, occurring in 44.6% and 8.0%, respectively.

CONCLUSION

With adequate surgical skills, extracapsular cataract extraction with posterior chamber intraocular lens implantation offers good visual rehabilitation even under training conditions.

Blue-yellow colour vision in an onchocercal area of northern Nigeria

AIM

To determine if the City University Tritan Test is a useful addition to visual function assessment in rural communities in northern Nigeria.

METHODS

The study was a cross sectional survey. The participants were 8394 people, aged 5 years and over, living in 37 rural communities, mesoendemic and nonendemic for onchocerciasis, in Kaduna State in northern Nigeria. The main outcome measures were the detection of a defect in blue-yellow colour vision by two criteria: (1) failure with the City University tritan screening plates; (2) failure with the City University grading plates to identify severe tritan defects.

RESULTS

91% of those aged 10 years and above could perform the test. Below this age, there were difficulties in comprehension. The test showed good inter- and intraobserver agreement. After adjustment for confounders the odds of failing the screening plates were significantly increased in the presence of optic atrophy or glaucoma (3.55 (2.48-5.08) and 15.9 (4.22-60.2) respectively). There was a greater increase in the adjusted odds of failing the grading plates in the presence of optic atrophy or glaucoma (5.30 (2.97-9.45) and 8.87 (1.61-48.7) respectively). Cataract had a smaller effect on the screening plates, adjusted odds 1.63 (0.95-2.80).

CONCLUSION

Blue-yellow colour vision testing is a useful addition to visual function assessment in those aged 10 years and above in rural northern Nigeria, particularly in the detection of optic nerve disease.

Onchocercal eye disease and the impact of Mectizan treatment

Onchocerciasis continues to be a major cause of blindness, particularly in those sub-Saharan African countries which are outside the area of West Africa monitored by the Onchocerciasis Control Programme (OCP). Onchocercal ocular disease and blindness develop as a result of long exposure to onchocercal infection. Until 1987, suramin and diethylcarbamazine were the only drugs available for the treatment of onchocerciasis and they could not be used for community therapy because of their toxicity and the dosage schedules required. The registration of Mectizan (ivermectin, MSD) for treatment of human onchocerciasis in 1987, and the donation of this drug by Merck & Co. for as long as it is needed, provided a new opportunity for the safe treatment and control of the disease. The data available on the impact of repeated doses of Mectizan on ocular onchocercal disease indicate a significant reduction of ocular microfilarial loads and regression of early lesions of the anterior segment, including iridocyclitis and sclerosing keratitis. Such improvements are seen more rapidly when Mectizan is used than when onchocerciasis is limited by vector control alone. Mectizan treatment also has a beneficial effect on onchocercal optic-nerve disease and visual-field loss. Long-term maintenance of Mectizan therapy should lead to a reduction in the prevalence of blindness in endemic communities.

HLA-DQ alleles associate with cutaneous features of onchocerciasis. The Kaduna-London-Manchester Collaboration for Research on Onchocerciasis

Onchocerciasis is associated with a spectrum of cutaneous changes, ranging from clinically normal skin to acute and chronic pathology. An important aspect of disease expression may be the level of immune response to parasite antigens, which is likely to be regulated by MHC-encoded molecules. We therefore investigated HLA class I and class II phenotypes in Nigerian residents of an area endemic for onchocerciasis. All study subjects were carefully characterized for parasite load and skin pathology. Individuals with depigmentation had increased frequencies of DQA1*0501 and DQB1*0301 compared with persons with normal skin and high microfilarial load (NSHMF) (Odds Ratios 3.6 (95% CI 1.0 to 13.2) and 3.8 (1.0 to 15.2), respectively). Conversely, individuals with depigmentation had a decreased frequency of DQA1*0101 and Cw6 compared with NSHMF (Odds Ratios 0.2 (0.1 to 0.9) and 0.1 (0.02 to 0.8), respectively). When NSHMF subjects were examined by age, a further decrease in DQA1*0501 frequency and increase in DQA1*0101 frequency were observed in older NSHMF individuals. These results strongly suggest that there is an immunogenetic basis for the spectrum of cutaneous presentations in onchocerciasis and that HLA-DQ molecules are associated with the level of immune response to parasite antigens.

Visual field constriction as a cause of blindness or visual impairment

Reported are the results of a study of onchocerciasis in communities mesoendemic for savanna onchocerciasis in Kaduna State, northern Nigeria. The study involved 6831 individuals aged > or = 5 years who underwent an extensive screening examination for visual function including Friedmann field analysis. A total of 185 (2.7%) were bilaterally blind by acuity and an additional 28 (0.4%) were blind by visual field constriction. Also 118 (1.7%) individuals were visually impaired by acuity criteria. No criteria for visual impairment by field constriction have been established, and we therefore investigated three potential criteria. As a result, a further 60 (0.9%) individuals were identified with significant visual impairment due to field loss by the various definitions. Small islands of remaining peripheral field occurred in 50 individuals, while 40 individuals had marked reduction of binocular visual field below the horizontal meridian. Concentric visual field constriction to < 20 degrees was found in seven individuals. The WHO definition of blindness currently includes visual field damage criteria for blindness but not for visual impairment. Visual field loss is recognized as a major disability. We hope that these findings stimulate international discussion leading to the development of satisfactory definitions for visual impairment by visual field constriction.

Risk factors for optic nerve disease in communities mesoendemic for savannah onchocerciasis, Kaduna State, Nigeria

Ophthalmic examinations on 6831 individuals aged 5 years or more, living in 34 guinea savannah communities mesoendemic for onchocerciasis, in Kaduna State, Nigeria, revealed a relatively high prevalence (9%) of optic nerve disease (OND). Further investigations were performed to determine what proportion of this burden of OND might be due to onchocercal infection. Information on history of cerebro-spinal meningitis (CSM), past use of diethylcarbamazine (DEC) and chloroquine, consumption of cassava and locally produced alcohol was collected for all individuals by questioning. In addition, a nested case-control study of 81 cases of OND and 136 age and sex-matched controls was performed to investigate whether syphilis or a variety of other neurological disorders were responsible for a substantial proportion of cases of OND. Our data suggest that in this population, onchocercal infection is the single most important cause of OND and may account for 50% of all cases. Some 13% of cases were associated with signs suggestive of glaucoma. DEC use might be responsible for up to 30% of all OND. We found no evidence to suggest that any of the following are important causes of OND in the communities studied: CSM, syphilis, neurological syndromes such as polyneuropathy or other generalized neurological disease, consumption of raw cassava, consumption of locally prepared alcohol.

Impact of annual dosing with ivermectin on progression of onchocercal visual field loss

Reported are the results of a randomized, double-masked, placebo-controlled trial of annual ivermectin dosing in 34 rural communities, Kaduna State, northern Nigeria, where guinea savanna onchocerciasis is mesoendemic. A total of 939 individuals underwent Friedmann field analysis at the first examination and saw at least 19 spots in at least one eye. Of these, 636 (68%) completed a subsequent Friedmann field analysis 2-3 years later. The adjusted incidence rate ratio for the ivermectin group versus the placebo group was 0.64 (95% confidence interval (CI): 0.42-0.98). There was some evidence that the impact of ivermectin was greatest among those who had received one dose of ivermectin. The majority of the deteriorations occurred in eyes that gave evidence of optic atrophy at the first examination. An analysis restricted to individuals with optic atrophy at baseline indicated a reduction of 45% in the incidence of visual field deterioration in the ivermectin group (95% CI: 8-67%). Previous findings have shown that ivermectin has an impact on the incidence of optic atrophy. Our results indicate, for the first time, that ivermectin has a substantial impact on the progression of visual field loss among those with pre-existing optic atrophy.

Morphine-induced venodilation in humans

Morphine has been extensively used in the treatment of pulmonary edema, and its action is believed to be mediated in part by its ability to produce peripheral venodilation. This study investigated whether opiates produce venodilation in human hand veins and explored the underlying mechanism(s). Fifteen healthy volunteers (11 men and four women) were studied with use of the dorsal hand vein compliance technique. After preconstriction with the selective alpha 1-adrenergic receptor agonist phenylephrine, dose-response curves were constructed to (1) opiate receptor agonists morphine (1 to 30 micrograms/min) or fentanyl (0.07 to 1 microgram/min), (2) a combination of morphine and the mu-opiate receptor antagonist naloxone, and (3) morphine and a combination of histamine (H1 and H2) receptor antagonists. Infusion of morphine caused venodilation in a dose-dependent manner, whereas fentanyl did not produce venodilation. Coinfusion of naloxone and morphine impaired the venodilation only slightly. Coinfusion of the H1- and H2-antagonists completely abolished the venodilatory effect of morphine. These results suggest that the venodilatory effect of morphine is mediated through histamine release and that mu-opiate receptors have little or no involvement in this process.

Maintaining compliance to ivermectin in communities in two West African countries

We have investigated various aspects related to managing wide-scale ivermectin distribution schemes within randomized controlled trials in communities where onchocerciasis is endemic. Multiple logistic regression analysis of determinants of compliance to five doses of ivermectin in 589 people in Sierra Leone showed independent significant associations with leopard skin depigmentation, the severity of side effects of treatment, fulfilling the exclusion criteria for treatment, and long-term residence in the community. These results are useful for tailoring health promotion messages in Sierra Leone, but the associations may differ in other West African societies. In Nigeria 1847 people were interviewed about various subjective responses, including itching. None of these showed clear improvement after three years of ivermectin treatment. Positive comments about treatment were generally non-specific and similar in the placebo and ivermectin groups. Negative comments were usually related to adverse reactions, especially itching and rash, and were more common after ivermectin. The lack of any benefit attributable to ivermectin that is discernible to its recipients may make it difficult to maintain the high compliance rates needed for long periods if mass dosing programmes are to have a lasting impact on onchocerciasis. In addition, no consistent effects of ivermectin were found by measuring visual acuity, height, weight or haematocrit in comparison with placebo. This may indicate that evidence of clinical impact is very slow to develop and is hard to measure using simple objective methods after only three doses of treatment. At present it seems that parasitological, entomological and detailed ophthalmological or dermatological methods are required to demonstrate the impact of ivermectin treatment in the medium-term.

Human onchocerciasis in Nigeria: isotypic responses and antigen recognition in individuals with defined cutaneous pathology

Antigen (Ag)-specific isotype responses to Onchocerca volvulus Ag (OvAg) were assessed by enzyme-linked immunosorbent assay and immunoblot in 123 residents of a mesoendemic area in northern Nigeria and 16 Nigerians from a nonendemic area. Individuals from an endemic area were divided into six groups on the basis of cutaneous onchocercal pathology: acute papular onchodermatitis (APOD), chronic papular onchodermatitis (CPOD), lichenified onchodermatitis (LOD), atrophy (ATR), depigmentation (DPM) and normal skin, high microfilarial load (NSHMF). Immunoglobulin (Ig)G1-4 levels were all significantly associated with residence in an endemic area after controlling for age and sex (all P values = 0.0001). Both IgG1 and IgG3 were significantly associated with onchocercal clinical category after controlling for age, sex, and microfilarial load (P = 0.0031 and 0.0035, respectively). The IgG1 and IgG3 responses were both highest in LOD and lowest in NSHMF and ATR, respectively. A significant inverse association was found between IgG1 levels and microfilarial load after controlling for age, sex, and clinical category (P = 0.0061). On immunoblotting, 20 (44.4%) of 45 individual onchocerciasis sera contained IgG4 antibodies against a band of 29-31 kD, which was not recognized by pooled sera from individuals with other filarial infections. There was heterogeneity of antigen recognition within each of the onchocercal clinical groups, which together with the small numbers examined by immunoblotting, limits interpretation. Nevertheless, some differences in patterns of antigen recognition were found between the onchocercal groups. The LOD group demonstrated prominent immunoreactivity in IgG1 and IgG3 while a general paucity of low molecular weight reactivity was seen with NSHMF in IgG1-3 subclasses, but there was no specific banding pattern that differentiated NSHMF from those with pathology. Comparison of microfilariae-positive (mf+) and mf- individuals with onchocercal skin disease revealed significantly higher levels of all IgG subclasses and higher overall scores on semiquantitative assessment of immunoblots for IgG1, IgG2, and IgG4 for mf+ individuals. Differing isotypic responses may play a role in the pathogenesis of the clinical spectrum of cutaneous onchocerciasis.

Red-dot card test of the paracentral field as a screening test for optic nerve disease in onchocerciasis

A new screening test for optic nerve pathology is described, consisting of a series of four red targets presented at an angle of 12 degrees in the paracentral field above and below the horizontal meridian. Nonperception and desaturation of the targets are recorded. Inter-observer variability studies found a kappa value = 0.8. A total of 6831 individuals aged > or = 5 years in communities that were mesoendemic for savanna onchocerciasis in Kaduna State, northern Nigeria, were screened using the test. Of the participants 22% were unable to complete the test; almost two-thirds of these (62%) were aged 5-8 years. After exclusion of those visually impaired or blind according to WHO criteria and those unable to complete the test, the test showed a sensitivity of 40% and a specificity of 98% for optic nerve disease when inability to visualize one or more targets was used as the definition of test failure. The sensitivity increased to 54% with a specificity of 96% when the criterion for failure included desaturation of one or more targets. These values compare favourably with those for other available screening methods. The test took 1-2 minutes to perform and was readily accepted by patients and nurses.

Ivermectin dosing based on physical appearance

Ivermectin is a safe and effective microfilaricide which has been shown to have a beneficial impact on some onchocercal eye lesions. Current requirements for the distribution of ivermectin are that patients be weighed, and that their dose be determined according to their weight. This requirement increases the cost of distributing the drug to communities in need of treatment and, when scales breakdown, may lead to the suspension of distribution. Data are presented on a simple, alternative method of dose assessment based on the physical appearance of the patient. Fifteen assessors achieved an overall level of agreement with the weight-based schedule of 86% on a sample of 6420 patients. The level of agreement varied between assessors, from 73% to 95%. About 6% of the population would have received doses outside the range of the current weight-based schedule. We believe that the current insistence that each individual's dose of ivermectin be determined by weighing will hamper efforts to distribute the drug to those most in need of it and that our data indicate that workers can be trained to distribute ivermectin safely without weighing every individual. We would welcome confirmation of our findings from other populations.

Ivermectin and onchocercal optic neuritis: short-term effects

In 1982 the macrocyclic lactone, ivermectin, was first tested in human patients with onchocerciasis. It has since undergone phase I to IV trials and is now being widely distributed in onchocercal areas. The previous microfilaricide, diethylcarbamazine citrate (DEC), is known to precipitate or exacerbate active optic neuritis in some onchocercal patients, as part of a wider inflammatory response (the Mazzotti reaction). Ivermectin may also cause a mild reaction, especially in people with high microfilarial loads. Few data are available concerning the effect of ivermectin on active optic neuritis. A large, randomised, double-masked, phase IV trial is reported. Individuals were screened for evidence of optic nerve disease (OND), and those identified as possible cases of OND underwent detailed ophthalmic examination, including fluorescein angiography, before being dosed with ivermectin or placebo. A total of 6831 persons were screened of whom 856 (13%) underwent angiography prior to dosing. At 7-14 days after dosing an attempt was made to re-examine 50% of adults over the age of 20 years, including all those with OND. Six hundred and eighty-eight repeat or new angiograms were performed. During this period, 5 new cases of active optic neuritis and one case of exacerbation of existing optic neuritis were identified. Five of these individuals had received placebo and one ivermectin. Two individuals with optic neuritis before dosing had improved after 7-14 days. One had received placebo, the other ivermectin. Ivermectin does not appear to precipitate or exacerbate optic neuritis at a period of 7-14 days.

Distribution and aetiology of blindness and visual impairment in mesoendemic onchocercal communities, Kaduna State, Nigeria. Kaduna Collaboration for Research on Onchocerciasis

During a field trial of ivermectin in Kaduna State, 6831 people age 5 years and above, living in 34 mesoendemic onchocercal communities in Kaduna State, northern Nigeria, were examined for ocular disease. Visual function assessments included tests of visual acuity and visual fields. A total of 185 individuals (2.7%) were bilaterally blind by acuity criteria with a further 28 blind by field constriction. The overall prevalence of blindness was 3.1%. A further 118 individuals were visually impaired by WHO criteria. Examination for the cause of blindness revealed that 43% of eyes in bilaterally blind patients were blind due to onchocerciasis. A further 11% were blind from optic atrophy much of which was probably onchocercal in origin. Glaucoma was the next most common cause of blindness in the bilaterally blind (11%). Only 6% of eyes were blind from cataract as the primary cause. In the visually impaired population cataract was the most common primary cause of impaired/blind eyes (31%), followed by onchocerciasis (19%) [corrected].

A clinical classification and grading system of the cutaneous changes in onchocerciasis

Although onchocerciasis is one of the most important diseases of the skin and eye in the tropical world, to date there has been no formal consensus regarding the description and terminology of skin lesions. Furthermore, the contribution of cutaneous pathology to the morbidity and socio-economic effects of the disease has been largely neglected. We present a clinical classification and grading system for recording the cutaneous changes of onchocerciasis, and propose that this system be used as a standard method of description to convey clinical information between workers in all endemic areas to assist local and comparative research.

An immunohistochemical analysis of onchocercal nodules: evidence for an interaction between macrophage MRP8/MRP14 and adult Onchocerca volvulus

We have used a panel of MoAbs to investigate the phenotype of macrophages and other leucocytes infiltrating onchocercal nodules. Nodules were removed from individuals at the end of the second year of a community-based, placebo-controlled trial of annual ivermectin chemotherapy in northern Nigeria. No significant differences were seen in the distribution and phenotype of leucocytes in nodules from ivermectin- and placebo-treated individuals. Live adult worms were only seen in nine of the 21 nodules examined. Three regions were clearly discernible within nodules containing both live and dead worms; an outer fibrovascular capsule (zone A), an inner adult worm bundle with surrounding hyaline extracellular matrix interspersed with solitary cells (zone B), and a dense cellular infiltrate surrounding and in contact with a variable proportion of the worm (zone C). Macrophages were the predominant cell type in all zones of the nodule. Those in zone B were distinguished by their dendritic morphology and strong reactivity with MoAbs directed against class II molecules, FcRI (CD64) and CD68, whereas macrophages in zone C were larger, more heterogeneous in shape, and were distinguished by strong reactivity with MoAbs directed against CR4 (CD11c, CD18) and MRP8/MRP14, and with MoAb24. T cells were found primarily in zones A and C, whilst eosinophils were found in only six nodules. A unique staining pattern was seen using MoAbs reacting with the calcium-binding protein MRP8/MRP14. Most macrophages in zones A and B were negative; however, where the occasional positive macrophage was seen in zone B, MRP8/MRP14 was also found around the cell and on the neighbouring worm surface, giving the impression that MRP8/MRP14 was being secreted onto the adult worm. Macrophages in zone C were also MRP8/MRP14-positive, and often the whole infiltrate was surrounded with extracellular MRP8/MRP14, with greatest concentration seen adjacent to the worm. MRP8/MRP14 was not identified on the surface of microfilariae (MF) within the same nodules. Since MRP8/MRP14 was seen on the adult worm in the absence of a leucocytic infiltrate, it may have an early role to play in the immune response to Onchocerca volvulus.

Reduction in incidence of optic nerve disease with annual ivermectin to control onchocerciasis

The safety and efficacy of ivermectin in the prevention of blindness from onchocerciasis have been established in many studies that have addressed the drug's effects on the front of the eye. We undertook a study with sufficient statistical power to detect an effect on optic nerve disease (OND), probably the main cause of blindness in the disorder. The trial was based in 34 mesoendemic communities in Kaduna State, Nigeria. Villagers aged 5 years and older were randomly assigned annual dosing with ivermectin or placebo for 3 years. Participants underwent medical and ophthalmological examinations before the first, third, and fourth treatments. 3522 villagers aged 15 and older were re-examined at least once. Skin-snip samples were taken at baseline for calculation of microfilarial load. The outcome measure was development of disc pallor accompanied by objective evidence of deterioration in visual function; 116 subjects (45 ivermectin-treated, 71 placebo-treated) showed such changes during the trial. The incidence rate ratio (ivermectin vs placebo) was 0.90 (95% CI 0.54-1.51) for subjects with loads of 0-10 mf (microfilariae) per mg skin and 0.52 (0.29-0.93) for subjects with more than 10 mf/mg. The incidence rate ratio varied little when account was taken of age, sex, presence of pre-existing disc pallor in one eye, previous use of diethylcarbamazine citrate, or doses of ivermectin or placebo received. There was evidence that ivermectin reduced the incidence of OND in subjects with microfilarial loads above 10 mf/mg but had little effect in those with lower loads. Sustained annual delivery of ivermectin could prevent a substantial proportion of onchocercal blindness in mesoendemic communities.

Ivermectin dose assessment without weighing scales

Described are two alternatives to the weighing of patients for assessing the dose of ivermectin for use in mass chemotherapy campaigns against onchocerciasis. The first method uses height to separate patients into four dosing categories (1/2, 1, 11/2 and 2 tablets), while the second involves estimating one of these dosing categories according to an individual's physical appearance, without making any measurements. Data for the height-based method were obtained from 6373 people who were taking part in a placebo-controlled trial of ivermectin in northern Nigeria. Use of an arbitrary trade-off of approximately 100 people "overdosed" for every person "underdosed" would lead to 0.5% of the population being underdosed by 1/2 tablet, 46.5% being dosed correctly, 51.7% being overdosed by 1/2 tablet, and 1.2% being overdosed by 1 tablet. The physical appearance approach involved three observers and 779 subjects. A total of 82% of the observers' estimates were "correct", with all the incorrect dosing deviating by only 1/2 tablet from the dose that the subjects should have received.

Childhood malignancies of the eye and orbit in northern Nigeria

One hundred four histologically proven malignant tumors of the eye and orbit in children seen in Guinness Eye Clinic, Kaduna, Nigeria between 1975 and 1982 are presented. Retinoblastoma and Burkitt's lymphoma account for the majority of the tumors. The data are compared with those from Ibadan, Nigeria. Burkitt's lymphoma occurs less frequently in Kaduna, whereas the incidence of retinoblastoma is almost the same. Chloroma, which was not seen in Ibadan, accounted for 2.9% of the current series. Factors that may be contributory to the observed differences are discussed.

Neurofibromatosis of the head and neck: clinical presentation and treatment

The clinical features of neurofibromatosis of the head and neck in 28 Nigerians are presented. The disease produced varying degrees of cosmetic and functional deformity. Total excision of the lesions, where feasible, with skin grafting, when indicated, gave satisfactory cosmetic and functional results. Incomplete excision was unsatisfactory for all eyelid and other more extensive lesions. Intraoperative bleeding was prominent and postoperative follow-up poor.

Cryosurgery in the management of vernal keratoconjunctivitis

Forty-eight eyes of patients with bulbar vernal conjunctivitis and eight eyes of patients with severe tarsal vernal conjunctivitis were treated with cryopexy. A pointed probe with tip temperature of -35 degrees C was used for the bulbar application, while a round-ended probe with tip temperature of -70 degrees C was used for tarsal application after excision of large cobblestones. Immediate results were highly impressive, while observation over 36 months in some of the patients showed long-term relief or very marked reduction in frequency of exacerbations. Cryotherapy avoids the long-term use of topical corticosteroids in vernal conjunctivitis and is preferable in our largely illiterate population. This study shows that the method is effective and safe.

Ophthalmic needs of Nigerian factory workers

In a survey of two factories the potential ocular hazards identified were metal and other foreign body injuries, molten metal injury, radiation effects to the eye and chronic conjunctival irritation from cotton fluff in the atmosphere. Although protective eye devices were provided, they were not often worn, this failure resulting in six ocular accidents. It is recommended that nurses be trained to carry out the initial treatment of ocular accidents and the importance of accident records stressed. Reasons for the importance of preliminary ocular screening of workers are highlighted. Prevention of ocular accidents must be comprehensive to be effective and must necessarily involve management as well as employees.

The ocular health status of postprimary school children in Kaduna, Nigeria: report of a survey

In a study of 5,220 postprimary school children in Nigeria, 10.36% had one or more ophthalmic defects requiring attention. The common problems encountered were conjuctivitis, refractive errors, and muscle imbalance, most of which were either intermittent or incomitant. Low degree myopia is common even though high myopia is not frequently seen. Old uveitis and corneal opacities were found to cause gross visual defects in some students and early macular degeneration was detected in nin students. The responsibility of the school medical officer in treating early infective cases and in referring other more complicated cases to hospital is emphasized.

Ocular health status of Nigerian industrial workers

In an ophthalmic survey of 3676 industrial workers in Kaduna, Nigeria, 395 industrial workers had ocular defects. The anterior segment of the eye was mainly affected. A wide spectrum of other eye diseases was seen. Ninety-two workers had poor vision in one or both eyes or had totally lost the vision in one eye. Although considerable morbidity, especially in the form of chronic conjunctivitis, resulted from mechanical irritation of the eyes in one factory, industrial accident resulted in loss of vision in only two workers.

Congenital sclerocornea in Nigerian children

Four cases of congenital sclerocornea in Nigerian children are described. Two of these children are from the same family suggesting a genetical determination. A developmental anomaly with various manifestation and associated with other ocular abnormalities would appear to be the etiology. One of the cases also had extrophia vesicae, an association that has not been previously described.

Pattern of retinal diseases in Lagos

Although primary retinal detachments occur infrequently in Africans, retinal diseases are not so uncommon. Ninety-two out of 1,723 patients seen in the Lagos University Teaching Hospital Eye Clinic had retinal diseases, a prevalence of 5.3%. We have seen most of the diseases described in other countries but while sicklemia retinopathy and various types of tapetoretinal dystrophy constitute a problem, hypertensive and diabetic retinopathies are infrequently seen. Retinoblastoma is the only tumor encountered so far and would appear to be sporadic. Positive family histories are difficult to obtain in our patients. It is anticipated that more retinal diseases will be diagnosed as more people become literate and notice slight to moderate visual loss.

Tuberculous panophthalmitis

The case of a one-year-old Nigerian with tuberculous panophthalmitis is reported. He presented initially with a localised episceleral mass which was thought to be retinoblastoma due to rapid spread over the fundus induced by subconjunctival depromedrol. Histological examination of the enucleated eye showed that the lesion was due to tuberculosis. The subsequent favorable response of the ocular and radiological chest lesions to antituberculous therapy was quite remarkable. In contrast, there was an adverse response to radiotherapy which had followed enucleation on the strong suspicion of retinoblastoma. Not unnaturally, ocular tuberculosis was not thought of because of the rarity of ocular involvement with this disease. To our knowledge, this is the first case of its type reported from the African Continent.

Ocular findings in children with homozygous sickle cell anemia in Nigeria

The ophthalmological findings in 91 Nigerian children with homozygous sickle cell anemia is reported. While the most constant sign was abnormality of the conjunctival vasculature, seen in 74(81%) of the patients, retinal lesions were found in a total of 53(58%) patients. Only tortuosity of major vessels was seen in some patients but several others had more than one type of retinal lesion.

Retinal diseases in Nigerians--a preliminary report

Of 595 new patients seen in the Eye Clinic of Lagos University Teaching Hospital, twenty-seven had retinal diseases, a prevalence of 4.5% Seven of these patients had retinopathy associated with sickle cell haemoglobinopathy and another seven had macular degenerations. Other causes of retinal diseases are analysed and the findings compared with reports from other countries. It is suggested that haemoglobin electrophoretic fractionation should be done in young Nigerians presenting with retinal diseases.