Introduction

Acanthocheilonemiasis, one of the filarial diseases (nematodes), is rare and infectious. It is caused by a type of parasite called Acanthocheilonema perstans, which mostly originates from tropical areas, mainly Central Africa and some areas of South America. The disorder can affect both males and females equally. Here are some of the notable symptoms that can be used for self-diagnosis and confirmation of Acanthocheilonemiasis in individuals who frequently travel between endemic areas. These symptoms include itchy skin (pruritus), abdominal pain, chest pain, muscle pains (myalgias), and skin lumps.¹

Geographic distribution

General distribution around the globe

The most widespread form of the filarial disease, Bancroft Filariasis, is endemic in Africa. Meanwhile, other research illustrates that there is a very small number of different forms, which exist in the Pacific Islands and differ only in some minor details from the most widespread form. The infections primarily occur in the inland areas of those islands, where personal anti-mosquito precautions are insufficient, as filariasis is mostly spread by various insect hosts, mosquitoes, biting flies, and midges.² 

Acanthocheilonemiasis, as one of the endemic filarial diseases, shares a very similar pattern of geographic distribution and vectors of transmission as other filariasis diseases. Most cases of infection originate from Africa, with a few variations reported in South America, where it is spread by midges. Below are the general endemic areas of this rare and infectious disease.

Acanthocheilonemiasis in Africa

There is an obvious correlation between the distinct features of the climate and environment in Africa and the endemism of Acanthocheilonemiasis in African countries, because of the abundant biodiversity and its unique tropical and subtropical environment.

The abundant biodiversity (encourages species development)

The abundant ecosystems in African countries demonstrate a wide variety of species. At the same time, this large abundance encourages the development of both midges and parasitic worms, Acanthocheilonema Perstans, for spreading the disease, which increases the infection rate, as the midges can act as a vector host to Acanthocheilonema Perstans.

Unique tropical and subtropical environment (allows vector proliferation)

Midges have already developed strong adaptations to tropical and subtropical areas. These adaptations to African climates allow them to thrive in diverse ecological niches, which can be the ideal environment for vector proliferation. As a result, midges can survive and spread in most tropical areas. 

The data and report revealed by the Cleveland Clinic demonstrate the clinical and diagnostic features of the infected cases, of the total six patients received by the clinic. There is a notable commonality shown, as all six patients are from African countries, including countries in sub-Saharan Africa, extending primarily from West African countries bordering the Gulf of Guinea (Ivory Coast, Nigeria, and Equatorial Guinea) and from Gabon and Angola east through Central Africa to Kenya and Mozambique, with the presence of the parasitic worm, Acanthocheilonema Perstans.⁴

The report given by the Cleveland Clinic of six patients can be one piece of evidence to justify the rarity and endemism of Acanthocheilonemiasis, but further investigations are still necessary for a better understanding.

Filariasis in South America

As the disease is mainly transmitted through the parasite, Acanthocheilonema Perstans, it has been found in Brazil, Colombia, Argentina, and Venezuela. However, there are far fewer cases of infection in South American countries, compared to endemism in African countries, where it remains a rare and infectious disease.

Additionally, Mansonelliasis, another filarial disease in tropical areas that is very similar to Acanthocheilonemiasis, occurs along the northern coast of South America (Colombia, Venezuela, Guyana, Suriname, and French Guiana), in the Yucatán area of Mexico and on Trinidad and other Caribbean Islands, due to the presence of Mansonella Perstans. The prevalence exceeding 50% demonstrates the endemism of Mansonelliasis in South American countries.⁴ 

Epidemiology

Transmission

Acanthocheilonemiasis is transmitted through the bites of midges, which can act as a vector to carry the parasite Acanthocheilonema Perstans. The parasite stays in the human body in its adult form, and the adult worms live in the retroperitoneal connective tissues as well as large body cavities.²

Population at risk

The insect hosts are midges, which only bite in the dark, especially in endemic areas(mainly African and South American countries) where people sleep with the light on.³ In some communities in the endemic areas, the prevalence rate rises to over 50% sometimes.⁴

Clinical presentations

In most circumstances, the rare and severe symptoms will not develop unless the continual re-infection occurs over many years.³ Moreover, there is a variability of symptoms based on geographic distribution and affected population. Normally, notable and distinguishing symptoms include:

1. Asymptomatic cases: no symptoms
2. Symptomatic cases: Itching, fever, swelling, abdominal pain
3. Rare severe complications: pericarditis, hepatitis, and neuropsychiatric symptoms

Noted: The infections are normally more or less non-pathogenic and do not lead to severe symptoms.³

Diagnostic methods

1. Two common methods
   • Blood smear examination for microfilariae under the microscope in the laboratory, looking at the blood sample⁵
   • Serological tests look for the existence of antibodies in the blood sample⁵

2. Challenges existed during the diagnosis
   • Low parasite load in the blood sample: The concentration of microfilariae in the peripheral blood of infected individuals is often low for detection, which makes detection difficult, particularly if blood samples are not collected at the optimal time or if the volume of blood examined is insufficient​⁵
   • Asymptomatic Cases: Many infections are asymptomatic or present with very mild symptoms, leading to underdiagnosis and misdiagnosis​⁵
   • Nonspecific symptoms: Symptoms such as fever, itching, and localised swelling are nonspecific and overlap with many other tropical diseases like loiasis, onchocerciasis, and lymphatic filariasis​​.⁵

Public health impact

Socioeconomic burden on affected communities

1. Limited resources and poverty

Many endemic countries have limited financial and human resources to allocate towards public health sectors. This affects the implementation of effective disease control and prevention measures​. High levels of poverty can lead to insufficient healthcare infrastructure, limited access to clean water, poor hygienic situations, and malnutrition, all of which raise the susceptibility to infectious diseases​.¹

2. Global health priorities

Global public health priorities and funding are directed towards more widespread and more communicable diseases, leaving rare diseases with less attention and resources for research and control​.

Summary

In summary, Acanthocheilonemiasis, as a rare and infectious disease, is caused by parasitic infections by Acanthocheilonema Perstans, transmitted through midges as its vector. Most cases of the disease are distributed in African as well as South American countries, which causes endemism in these two areas; the prevalence rate in some communities even rises to 50% or above. Although the parasitic infection sounds severe and dangerous, the infections are more or less nonpathogenic, which seldom lead to severe symptoms.

FAQs

Will acanthocheilonemiasis develop or cause any severe symptoms?

The pathology signs and symptoms are minor for the vast majority of people. The serious lesions, which might cause endemic blindness or gross elephantiasis, occur only after continual re-infection over many years, as the pathology of filarial infection is progressive only as long as the patient is re-infected by insect hosts.

Are there any other filarial diseases which have similar symptoms to Acanthocheilonemiasis?

Mansonelliasis, which the parasite Mansonella Perstans causes, has very similar symptoms to Acanthocheilonemiasis.   

What can we do to prevent being infected?

The application of insecticides can help to reduce the population of midges, which lowers the transmission rate of the disease; meanwhile, personal protective measures, including the use of repellent, bed nets and wearing protective clothing, can reduce the chance of being bitten by midges.

How can we treat this disease?

The antiparasitic medications are essential, Diethylcarbamazine (DEC), and Ivermectin, which are treatments for acanthocheilonemiasis, which target both adult and microfilariae worms.  The other anti-inflammatory medication should be applied to ease the fever, itchy skin and swelling.