Oro-facial filariasis–A systematic review of the literature
Authors: Bytyqi Agnesa , Karas Chiara , Pechmann Klara , Ramharter Michael , Mischlinger Johannes 
Published: November 2024

Introduction
Filarial pathogens are described to inhabit and affect subcutaneous and lymphatic tissues of the human host. To date, little is known on how much oral health might be affected by filarial infections, even though involvement of the oro-facial region is pathophysiologically possible. Therefore, we conducted this systematic review of the literature to help reduce the current evidence gap. First, we reviewed the existing literature related to oro-facial filariasis and summarized all confirmed cases in detail. Second, we presented the demographic clinical characteristics of published oro-facial filariasis cases using descriptive statistics.

Methods
A comprehensive search was conducted using PubMed and Google Scholar to identify scholarly articles on oro-facial filariasis (PROSPERO: CRD42024551237). Clinical trial registries of clinicaltrials.gov and the Pan-African Clinical Trials Registry (PACTR) were checked for ongoing studies on oro-facial filariasis.
From clinical articles on filariasis and oro-facial health, patient-specific information was ascertained such as country of diagnosis, age, sex and symptoms of the patient, location of filarial disease manifestation, filarial worm species diagnosis, main clinical diagnosis, as well as main pathology and lastly therapy. Descriptive statistics were computed.

Results
The systematic search was conducted on 18.06.2024. Initially a total of 1,064 publications was identified. No registered study on oro-facial filariasis was found on large clinical trial registers. After sequentially assessing abstracts and full-texts for eligibility, the analysis population was reduced to 68 articles amounting to 111 cases of oro-facial filariasis. Published articles which were identified and ultimately selected consisted solely of case reports, or case series; not a single epidemiological study was found in the published body of literature. Published data on oro-facial filariasis was identified from as early as 1864 until 2022. The median age of oro-facial filariasis cases was 39 years (range: 1 year to 80 years) and evenly distributed between the two sexes (49% [54/110] female and 51% [56/110]; sex not reported for one case). The vast majority of identified cases was on oro-facial dirofilariasis (92% [102/111]), followed by lymphatic filariasis (2.5% [3/111]), lymphatic filariasis with squamous carcinoma (2.5% [3/111]), and lastly by onchocerciasis (1% [1/111]). Although in 34% (38/111) of articles there was no clear description of the main pathology of oro-facial filariasis, all of the remaining 73 articles described nodules or swellings. Asymptomatic manifestations constituted almost 75% (55/73) and only about 25% (18/73) of articles described a symptomatic case.

Conclusion
Although filarial diseases are to date not generally regarded as being associated with oral health problems this assumption might not be justified. This comprehensive systematic review was conducted to detect and collate all published studies on oro-facial filariasis. The fact that only case reports, or case series were identified suggests that this constitutes a neglected field of research. Cases identified in the published literature indicate that the vast majority of published oro-facial, filarial case reports were cases of dirofilariasis. Among the published studies, oro-facial filariasis manifested exclusively as nodules or swellings in different tissue locations. These nodules and swellings were mostly asymptomatic and therefore, cancer is an important differential diagnosis.