Besides fever and diarrhea, skin diseases are the third most common cause of morbidity in returning travelers after a stay in a tropical country. Approximately one- quarter of these dermatological symptoms can be referred to a classical tropical disease. The majority are of infectious origin. Often only the clinical appearance leads to the diagnosis of a tropical disease as myiasis, cutaneous larva migrans, tungiasis or cutaneous leishmaniasis. Not infrequently the dermatological symptoms lead to the diagnosis of a primarily systemic tropical disease. For example, an eschar with or without a rash might lead to the diagnosis of a South African tick bite fever caused by Rickettsia africae days before serology may turn positive. Less common tropical skin diseases such as lymphatic filariasis and loiasis need to be considered in returning long-term travelers and immigrants.

There is growing interest and commitment to the control of schistosomiasis and other so-called neglected tropical diseases (NTDs). Resources for control are inevitably limited, necessitating assessment methods that can rapidly and accurately identify and map high-risk communities so that interventions can be targeted in a spatially-explicit and cost-effective manner. Here, we review progress made with (1) mapping schistosomiasis across Africa using available epidemiological data and, more recently, climate-based risk prediction; (2) the development and use of morbidity questionnaires for rapid identification of high-risk communities of urinary schistosomiasis; and (3) innovative sampling-based approaches for intestinal schistosomiasis, using the lot quality assurance sampling technique. Experiences are also presented for the rapid mapping of other NTDs, including onchocerciasis, loiasis and lymphatic filariasis. Future directions for an integrated rapid mapping approach targeting multiple NTDs simultaneously are outlined, including potential challenges in developing an integrated survey tool. The lessons from the mapping of human helminth infections may also be relevant for the rapid mapping of malaria as its control efforts are intensified.

With increasing migration tropical diseases such as Loa loa infections are becoming more frequent in Europe. While the ocular diagnosis is usually straight forward, systemic work-up and treatment requires an interdisciplinary approach. We review the diagnostic and therapeutic work-up of ocular Loa loa infections based on a series of 4 cases that presented between 1998 and 2004.The first symptoms in all cases were ocular irritations occurring 2 months to 8 years after a trip to West Africa. One case presented with a swollen upper eyelid without a visible worm. In three patients microfilariae were detected in the blood.In two cases visible subconjunctival worms could be removed under the slit lamp. Three cases required systemic treatment as inpatients while one case could be observed without systemic treatment. All 4 cases had a favourable outcome with complete eradication of the disease.Surgical removal of adult Loa loa worms from the subconjunctival space only improves the ocular symptoms. An interdisciplinary approach (ophthalmology, infectious disease and parasitology) for a systemic work-up and treatment is usually required.

Evidence is accumulating from experimental and human studies that genetic factors are involved both in the control of infectious diseases and in the regulation of infection levels and clinical presentation. So far few studies have investigated the role of these genetic factors in human infection by the filarial parasite Loa loa. We present a segregation analysis on 74 nuclear families who live in the tropical rainforest of southern Cameroun and are exposed to homogeneous loiasis transmission. The results indicate that there is a genetic predisposition to be microfilaraemic and that predisposed subjects might be genetically unable to mount an efficient immune response against loiasis antigens. This individual susceptibility could explain at least in part why the prevalence of infection (microfilaraemic individuals) does not usually exceed 30% of the exposed population in hyperendemic regions. Further genetic studies, based on linkage analysis using both familial information and genetic markers, will help to identify the nature of the genetic factors predisposing to microfilaraemia.

A 40-yr-old West African man presented acutely with pleural effusion. Cytologic evaluation of the pleural fluid revealed Loa loa microfilariae. No additional etiology for the pleural effusion could be identified, and antifilarial treatment with diethylcarbamazine led to a rapid resolution of the patient's symptoms and pulmonary abnormalities. Loa loa must be considered as a treatable cause of eosinophilic pleural effusions in persons from endemic areas of West and Central Africa.

The effect of diethylcarbamazine citrate (DEC) treatment (43-150 mg kg-1 daily for 12-21 days) on adult Loa worms in five drills (Mandrillus leucophaeus) is described. In individual monkeys, between one-third and all of the adult worms survived the treatment, and most of the surviving females were still producing live microfilariae. These experiments provide direct evidence which may explain the common clinical experience that single courses of DEC do not always succeed in eliminating the signs and symptoms of loiasis in humans. Further work on the chemotherapy of loiasis in monkeys, using DEC and other filaricides, might improve the treatment of this disease.

To determine whether infection with Loa loa could be prevented in temporary residents of endemic areas, we conducted a randomized, double-blind, placebo-controlled trial of diethylcarbamazine as a chemoprophylactic agent. Diethylcarbamazine (300 mg) or placebo was taken orally once a week by Peace Corps volunteers serving in Gabon, Cameroon, and the Central African Republic. The participants were assessed clinically and with serologic and parasitologic testing before and yearly during their two years of service. One hundred one persons satisfactorily completed the study. In Gabon (where exposure to the parasite was heaviest), 6 of 20 volunteers (30 percent) in the placebo group had clinical disease, as compared with none of 16 (0 percent) in the diethylcarbamazine-treated group (P less than 0.02). Of those taking placebo, 10 of 20 (50 percent) became seropositive for antifilarial IgG antibody, as compared with 2 of 16 (12 percent) in the drug-treated group (P less than 0.02). Exposure to the parasite appeared to be much lower among the 65 Peace Corps volunteers in Cameroon and the Central African Republic. No volunteer in either group in these countries had overt loiasis; 2 of 40 (5 percent) in the placebo groups in Cameroon and the Central African Republic seroconverted, as compared with none of 25 (0 percent) of those receiving diethylcarbamazine. Occasional nausea was the only symptom significantly associated with the prophylactic drug regimen. We conclude that diethylcarbamazine given orally once weekly can be an effective, acceptable chemoprophylactic agent to prevent loiasis in temporary residents of regions of Africa where Loa loa is endemic.

With reference to an exceptional observation of arthritis due to Loa loa filariasis with eosinophils predominating in the joint fluid, the causes of such joint effusions are reviewed. These effusions are neither specific of nor consistent in articular manifestations of parasitic infections. Demonstration of a high eosinophil count in joint fluid should always suggest a parasitic disease. However, synovial eosinophilia may be found in many other conditions and may even appear to be primary.