Splenectomy for suspected malignant lymphoma in two patients with loiasis

Evaluation of a novel biplex rapid diagnostic test for antibody responses to Loa loa and Onchocerca volvulus infections

BACKGROUND

Endemic to Central Africa, loiasis, caused by the vector-borne worm Loa loa, affects approximately 10 million individuals. Clinical manifestations include transient angioedema (Calabar swellings), migration of the adult worm under the eye conjunctiva (eye worm) and less specific general symptoms. Loiasis presents a significant public health challenge because L. loa-infected individuals can develop serious adverse events after taking ivermectin, the drug used to combat onchocerciasis. In this context, alternative interventions and rigorous diagnostic approaches are needed. Diagnosing loiasis is challenging because its main clinical manifestations are sporadic and non-specific. The definitive diagnosis relies on identifying adult worms migrating beneath the conjunctiva, or microfilariae (pre-larvae) in blood smears. However, "occult loiasis" (infection without blood microfilariae) is frequent. Serological rapid antibody diagnostic tests (ARTs) can provide an alternative diagnostic method. We compared a novel ART simultaneously targeting onchocerciasis (IgG4 to Ov-16 and OvOC3261, test line 1) and loiasis (IgG4 to L1-SXP-1, test line 2), called IgG4-SXP-1 biplex test) to the already established Loa-ART (all IgG isotypes to Ll-SXP-1, called pan-IgG-SXP-1 test).

METHODOLOGY

Blood samples underwent both ARTs, read qualitatively and semi-quantitatively. Additionally, blood smears, skin snips, Kato-Katz method for soil-transmitted helminthiases identification and eosinophilia measurements were performed. Questionnaires gathered demographic details and loiasis-related signs. ARTs performance was compared using specific loiasis-related signs and microfilaremia as references. Discordances between the two ARTs were investigated using logistic regression models.

PRINCIPAL FINDINGS

Out of 971 participants, 35.4% had L. loa microfilaremia, 71.9% had already experienced loiasis-related signs, 85.1% were positive in the pan-IgG-SXP-1 test and 79.4% were positive in the IgG4-SXP-1 biplex test. In the microfilariae-positive population, the sensitivity of the rapid tests was 87.4% for the pan-IgG-SXP-1 test and 88.6% for the prototype IgG4-SXP-1 biplex test. Sensitivity was similar for both ARTs when using eye worm or Calabar swelling as references, but diagnostic performance varied based on microfilaremia levels and occult loiasis. Overall, IgG4-SXP-1 biplex test demonstrated a sensitivity of 84.1% and specificity of 47.6% for loiasis compared to the pan-IgG-SXP-1 test, leading to a Kappa coefficient estimated at 0.27 ± 0.03 for the qualitative results of the 2 ARTs. In the group that tested positive with the Pan-IgG test but negative with the IgG4-specific test, there was a lower prevalence of STH infection (p = 0.008) and elevated eosinophilia (p<0.001) compared to the general tested population.

CONCLUSION/SIGNIFICANCE

The sensitivity of each test was good (84-85%) but the diagnostic agreement between the two ARTs was poor, suggesting that IgG and IgG4 antibody responses should be interpreted differently. The assessment of the innovative rapid diagnostic IgG4-SXP-1 biplex test, designed for onchocerciasis and loiasis, shows encouraging sensitivity but underlines the necessity for further in vitro assessment.

Focal spleen lesions in loiasis: A pilot study in Gabon

BACKGROUND

Infection with the filarial nematode Loa loa, endemic in Central and Western Africa, has been associated with increased morbidity and mortality. A number of reports described the presence of spleen nodules, originating from degenerating microfilariae, in humans and animals infected with L. loa. The long-term consequences of this process on individuals chronically exposed to infection in terms of spleen function and possible link with excess mortality are unknown. The aim of this study was to evaluate the prevalence of focal spleen lesions, their evolution over time, and markers of spleen function, in individuals with L. loa infection living in highly endemic areas of Gabon.

METHODOLOGY/PRINCIPAL FINDINGS

This was a cross-sectional study followed by a longitudinal study of the subset of individuals with spleen nodules. Two hundred sixteen participants from Ngounié and Moyen-Ogooué provinces of Gabon, reporting a history of eyeworm migration and/or Calabar swelling, were included. Participants were categorized into infected microfilaraemic with low (N = 74) and high (N = 10) microfilaraemia, and symptomatic amicrofilaraemic (N = 132), based on blood microscopy. Howell-Jolly bodies in erythrocytes, as indirect marker of spleen functional impairment, were within normal ranges. On ultrasound, no evident signs of spleen fibrosis or hypotrophy were observed. Multiple spleen hypoechoic centimetric macronodules were observed in 3/216 participants (1.4%), all with microfilaraemic L. loa infection (3.4% of microfilaraemics); macrondules disappeared at the 6-months follow-up examination in 2/3 individuals. Spleen hypoechoic micronodules, persisting at the 6-months follow-up, were detected in 3/216 participants (1.4%), who were all amicrofilaraemic.

CONCLUSIONS/SIGNIFICANCE

Transitory spleen macronodules are present in a small but consistent proportion of individuals with microfilaraemic loiasis, appearing a rather benign phenomenon in terms of impact on spleen morphology and function. Their occurrence should be taken into consideration to avoid misdiagnosis and mistreatment. Prevalence and significance of spleen micronodular ultrasound patterns in the general population would be also worth evaluating.

A Rare Co-existent Case of Splenic Microfilariasis and Pancreatic Solid Pseudopapillary Epithelial Neoplasm - A Double Jeopardy!

Filariasis is a major public health concern in tropical and subtropical countries like India with Wuchereria bancrofti accounting for 90% of lymphatic filariasis. Rarely observed are extra lymphatic manifestations caused by interaction of immune system with microfilaria and their diffusible products. Among various organs involved, splenic involvement is a rare extra lymphatic manifestation of filariasis and can masquerade clinicoradiologically as metastasis when associated with a known malignancy or as a primary malignancy like lymphoma. Hereby, we present an unusual case of coincidence of splenic filariasis with pancreatic solid pseudopapillary epithelial neoplasm in a 20-year-old woman associated with peripheral blood eosinophilia.

The African eye worm: current understanding of the epidemiology, clinical disease, and treatment of loiasis

Loa loa, the African eye worm, is a filarial pathogen transmitted by blood-sucking flies of the genus Chrysops. Loiasis primarily affects rural populations residing in the forest and adjacent savannah regions of central and west Africa, where more than 20 million patients are chronically infected in medium and high transmission regions. For a long time, loiasis has been regarded as a relatively benign condition. However, morbidity as measured by disability-adjusted life-years lost might be as high as 400 per 100 000 residents, and the population attributable fraction of death is estimated at 14·5% in highly endemic regions, providing unequivocal evidence for the substantial disease burden that loiasis exerts on affected communities. The clinical penetrance of loiasis is variable and might present with the classic signs of eye worm migration or transient Calabar swellings, but might include common, unspecific symptoms or rare but potentially life-threatening complications. Although adult worm migration seems most closely linked to symptomatic disease, high levels of microfilaraemia are associated with clinically important complications and death. Loiasis remains difficult to diagnose, treat, and control due to an absence of reliable point-of-care diagnostic assays, safe and efficacious drugs, and cost-effective prevention strategies. This Review summarises the major advances in our understanding of loiasis made over the past decade and highlights the many gaps that await to be addressed urgently.

Spleen nodules in Loa loa infection: re-emerging knowledge and future perspectives

Loiasis, the infection with the vector-borne filarial nematode Loa loa, is widely distributed in central and west Africa. Long considered a rather benign infection, recently loiasis with high microfilarial burden was associated with increased mortality risk. Eyeworm and Calabar swelling are pathognomonic signs of the infection, but other atypical, non-specific manifestations can also occur. For instance, splenic nodules have been seldom reported. In this Grand Round, we report two cases of loiasis in migrants who presented with spleen nodules, which could be followed up over time (up to 27 months) with multiple imaging techniques until their resolution. We comment on the clinical implications of these observations, including differential diagnosis with similar imaging findings, and critically review the evidence of spleen involvement in loiasis and other filarial infections.

Imported Loa loa filariasis: three cases and a review of cases reported in non-endemic countries in the past 25 years

OBJECTIVES

The aim of this study was to highlight the increasing chance of Western physicians encountering patients (both immigrants and expatriates/travelers) seeking help for loiasis.

METHODS

We describe three cases of imported loiasis observed at two hospitals in Italy and France, and present a review of all previously published cases in the medical literature in the last 25 years (1986-2011). The search was performed using PubMed and Scopus databases using the terms "Loa loa" AND "loiasis".

RESULTS

We reviewed 101 cases of imported loiasis of which 61 (60.4%) were reported from Europe and 31 (30.7%) from the USA. Seventy-five percent of infestations were acquired in three countries: Cameroon, Nigeria, and Gabon. Overall, peripheral blood microfilariae were detected in 61.4% of patients, eosinophilia in 82.1%, eye worm migration in 53.5%, and Calabar swellings in 41.6%. However, Calabar swellings and eosinophilia were more common among expatriates/travelers, whereas African immigrants were more likely to have microfilaremia. Eye worm migration was observed in a similar proportion in the two groups. Only 35 patients (including the three described here) underwent clinical follow-up for a median period of 10.5 months (range 1-84 months); clinical relapse occurred in three of these patients and persistence or reappearance of blood microfilaria in another two.

CONCLUSIONS

Due to increasing travel and the migration of people from the endemic countries of West Africa to Europe and the USA, we speculate on the possible emergence of loiasis. Western physicians should be aware of the typical (eye worm migration and Calabar swellings) as well as unusual clinical presentations.

Case report: Loiasis with peripheral nerve involvement and spleen lesions

Loiasis, which is caused by the filarial nematode Loa loa, affects millions of persons living in the rainforest areas and savannah regions of central Africa. Typical manifestations are calabar swellings and the eyeworm. We report a case of loiasis with unusual clinical complications: a peripheral neuropathy and focal hypo-echogenic lesions of the spleen, which disappeared after treatment with albendazole and ivermectin. The literature reports that L. loa infection can be associated with various manifestations, some of them being serious. More information is needed to better characterize the protean manifestations of the disease in loiasis-endemic areas to evaluate the true incidence of loiasis.

Is ultrasound a useful adjunct for assessing malaria patients?

The value of ultrasonography as an adjunct for diagnosis and monitoring malaria was investigated. In all, 118 patients (male/female 65/53; age 2-78 years, median 29 years) with malaria underwent a standardised abdominal ultrasound examination at baseline. In 62 out of 118 patients, ultrasonography was repeated 21 days later. In the results at baseline, huge splenomegaly with firm organ consistency, consistent with hyperreactive malarious splenomegaly syndrome, was observed in two Cameroonese children. In the other 116 patients, the most common finding was non-specific splenomegaly (96/116, 82.76%), occurring more frequently in non-immune patients (71/78, 91.03%) than in patients who had grown up in malaria-endemic areas (25/38, 65.79%; P<0.002). No correlation was found between liver or spleen size and any clinical parameter. The results on day 21 show that, although splenomegaly after therapy persisted more frequently in patients with malaria recrudescence or relapse (8/8, 100%) than in patients cured (32/54, 59.26%; P<0.0421), the practical value of this finding is questionable. Ultrasonography cannot be regarded as a first-line diagnostic method in patients with malaria.

Ultrasound in tropical and parasitic diseases

CONTEXT

Migration and worldwide travel mean that western clinicians and radiologists more and more face imported tropical diseases. Diseases with unclear signs and symptoms are likely to be investigated with ultrasound. Many tropical diseases have particular ultrasonographic features that are not familiar to the examiner and which may lead to further unnecessary or even harmful diagnostic investigations. In developing countries, ultrasound machines are becoming more widely distributed and are fairly cheap. Portable devices allow field use of ultrasound for population studies and individual diagnosis of tropical diseases.

STARTING POINT

Recently, WHO introduced a standardised classification of ultrasonographic images of cystic echinococcosis (Acta Trop 2003; 85: 253-61), to obtain comparable results in patients worldwide and to link disease status with each morphological type of echinococcosis cyst. WHO also defined guidelines for the puncture, aspiration, injection of ethanol, and re-aspiration of such cysts. Ultrasound allows diagnosis of schistosomiasis-induced periportal fibrosis and bladder abnormalities. Liver abscesses can be differentiated from other focal lesions such as cysts or neoplasms. For amoebic abscesses, invasive procedures are usually not required. In doubtful cases ultrasound-guided puncture can give adequate material for microscopy and culture. Helminths (eg, ascaris), flukes, and filariae can be seen directly with ultrasound. Filaria-induced damage also includes hypoechogenic splenic foci and ultrasonographic abnormalities due to tropical hypereosinophilia. WHERE NEXT? Classification of cysts and procedures that are less invasive than conventional surgery are being developed further for cystic echinococcosis. Novel methods are needed for the assessment of polycystic and alveolar echinococcosis. Ultrasound protocols for schistosomiasis are being evaluated for interobserver reliability, relation to clinical disease status, and power to predict complications. A WHO expert-group is also developing a standardised protocol for Asian schistosomiasis. International consensus on an algorithm for managing amoebic liver abscesses is needed.

Obligatory symbiotic Wolbachia endobacteria are absent from Loa loa

BACKGROUND: Many filarial nematodes harbour Wolbachia endobacteria. These endobacteria are transmitted vertically from one generation to the next. In several filarial species that have been studied to date they are obligatory symbionts of their hosts. Elimination of the endobacteria by antibiotics interrupts the embryogenesis and hence the production of microfilariae. The medical implication of this being that the use of doxycycline for the treatment of human onchocerciasis and bancroftian filariasis leads to elimination of the Wolbachia and hence sterilisation of the female worms. Wolbachia play a role in the immunopathology of patients and may contribute to side effects seen after antifilarial chemotherapy. In several studies Wolbachia were not observed in Loa loa. Since these results have been doubted, and because of the medical significance, several independent methods were applied to search for Wolbachia in L. loa. METHODS: Loa loa and Onchocerca volvulus were studied by electron microscopy, histology with silver staining, and immunohistology using antibodies against WSP, Wolbachia aspartate aminotransferase, and heat shock protein 60. The results achieved with L. loa and O. volvulus were compared. Searching for Wolbachia, genes were amplified by PCR coding for the bacterial 16S rDNA, the FTSZ cell division protein, and WSP. RESULTS: No Wolbachia endobacteria were discovered by immunohistology in 13 male and 14 female L. loa worms and in numerous L. loa microfilariae. In contrast, endobacteria were found in large numbers in O. volvulus and 14 other filaria species. No intracellular bacteria were seen in electron micrographs of oocytes and young morulae of L. loa in contrast to O. volvulus. In agreement with these results, Wolbachia DNA was not detected by PCR in three male and six female L. loa worms and in two microfilariae samples of L. loa. CONCLUSIONS: Loa loa do not harbour obligatory symbiotic Wolbachia endobacteria in essential numbers to enable their efficient vertical transmission or to play a role in production of microfilariae. Exclusively, the filariae cause the immunopathology of loiasis is patients and the adverse side effects after antifilarial chemotherapy. Doxycycline cannot be used to cure loiais but it probably does not represent a risk for L. loa patients when administered to patients with co-infections of onchocerciasis.