Introduction

What is acanthocheilonemiasis

Acanthocheilonemiasis is a rare tropical infectious disease caused by a multicellular parasite (filarial worm)¹ known as Acanthocheilonema perstans or Dipetalonema perstans, which belongs to a group of parasitic diseases known as filarial diseases (nematode).²

Where can I find acanthocheilonema perstans?

The parasite Acanthocheilonema perstans is commonly found in central Africa and in some areas of South America where the disease acanthocheilonemiasis is frequently found. This disease affects both genders (males and females) equally.²

Be vigilant

Most times those who are infected with the parasite show no signs or symptoms, primarily because the parasite lives in the human body and will not want to alarm the defence system of the body. However, with time some symptoms may develop such as;

• Itchy skin (pruritus)
• Abdominal pain
• Chest pain
• Headache
• Localised swelling (oedema)
• Muscle pains (myalgias)
• Swelling under the skin (subcutaneous)³ 

Due to Acanthcheilonemiasis rareness some of the disorders experienced may be similar to disorders caused by Filariasis as it is part of the rare parasitic disease group.⁴

Pathophysiology of acanthocheilonemiasis

Lifecycle of acanthocheilonema parasites

Transmission and development stages

The majority of human filarial nematodes have a lifecycle involving an insect vector. Microfilariae which are produced by adult female worms, circulate in the bloodstream but are incapable of maturing in the human body.⁵ So there is a need for another carrier vector to complete its maturation. Mosquitoes vectors feed on blood and ingest microfilariae from bloodstreams where the microfilariae mature into infective larvae. These larvae move to the mosquito mouth where they exit by puncture wounds of the vector where they migrate mate and mature.⁵

Immune response to the parasite

The fact that parasites stay longer than expected in the human system poses many problems.⁶ The human immune system is built to fight (defend) the body

The immunologic response experienced in Acanthchelionemiasis is the Type 2 immune response. Most people found in endemic areas are constantly reinfected with the parasites even after drug clearance.⁷ This aspect is the ability of sterile immunity in individuals.

In most infections, the body's immune system is modified to respond to and control the parasite load in the body.⁷

How does this disease affect other systems of the body?

Remember that because Acathechelonema is a rare tropical disease, there is little or no knowledge existing regarding the disease. However, they belong to the parasitic disease group (filarial) we expect that the symptoms and complications will be similar to other parasitic diseases of this group.

Below are examples of different systemic conditions arising from similar parasitic infections: 

Hematological complications

Eosinophilia

Eosinophils are part of the cells that make up the white blood cells. Eosinophilia is an increase in the number of circulating eosinophils in the blood per time (>500/mm³).⁸ 

 As the parasites (nematodes) stay long in the human system, they become comfortable and begin releasing microfilariae (small larvae parasites) into the bloodstream.⁹ These larvae can travel via the bloodstream and locate themselves at different parts of the body.⁹

Tropical lymphatic eosinophilia (TPE) occurs as the body's immune response to microfilariae trapped in the tissues of the lungs.⁹

How does TPE manifest?

If considered to have TPE, the most common signs seen are dyspnea, nocturnal cough, fever and wheezing⁹ with an eosinophil count of >3000/mm3.

TPE can further complicate leading to Pulmonary fibrosis.⁹

Lymphatic system involvement

Lymphadenopathy and lymphedema

Oedema can be described as excess fluid accumulation on any part of the body.² When adult parasitic worms dwell in the lymphatic vessels or lymph nodes, they induce lymphatic dilation which manifests as lymphoedema (severe forms known as elephantiasis), Adenolyphangitisa and hydroceles.¹⁰ This develops due to the host system's inflammatory reaction to the presence of the adult worm.¹⁰

Renal system

Nephropathy: proteinuria  

Parasitic diseases such as filariasis are associated with some of the worst kidney diseases such as acute kidney injury, tubular dysfunction and glomerulonephritis.¹¹

In most parasitic infections, patients have  asymptomatic proteinuria (increased levels of proteins in the blood) 

Amyloidosis is a disease caused by parasitic filarial worms which manifest with proteinuria, and nephrotic syndrome with variable degrees of renal failure.¹² However, proteinuria is mostly asymptomatic clinically in most filarial infections globally.

Hematuria

Blood found when passing out urine is known as Hematuria. It is not a very common complication of Acanthocheilonemiasis as most times hematuria is seen as a complication of bacterial infection of the urinary tract system.¹³

In most filarial cases, hematuria is microscopic¹³ and without microfilariae present in urine.¹⁴

Allergic reactions

Skin manifestations: rash, urticaria

Type 2 immune response is a pathologic allergic response leading to atopic dermatitis(skin rash), itching, pain and swelling. Moreover, the role of type 2 response has a protective ability to the body but could also cause anaphylaxis on exposure.⁷ These results form the body's defense system combatting the presence of parasites or its byproducts in the system.

Other systemic complications

Does acanthocheilonemiasis affect the central nervous system(CNS)?

This is not impossible though very rare. Most microfilariae when found in the CNS is potentially harmless, though in some cases it can lead to the affection of the limbs (paralysis) and the eyes.

Ocular complications

This can lead to blindness when larvae travel through the system and locate around the conjunctiva. The lesions are mostly found in the anterior sector of the eye and their severity is determined by the number of microfilariae found in the cornea

Hepatic complications

They cause a condition known as Hepatosplenomegaly, which is abnormally large spleens and liver

Cardiovascular system

The adult worm (nematode) may be found lodging in the tissues of the abdomen and chest causing inflammation and immune reactions. This results in inflammation of the lining of the lungs (pleuritis) and/or the membranes that surround the heart (pericarditis)³.

Diagnosis and management

Diagnostic methods

• Blood tests, imaging, and parasitological examination
• Most parasitic diseases are commonly diagnosed by detecting larvae in the stool, sputum, pleural fluid and in some cases human tissues¹⁵
• Chest x rays
• Thoracic surgical procedure may also be required to dismiss other lung diseases
• Full blood counts for patients with TPE³
•  Quantitative Serum immunoglobulin test increase in immunoglobulin E often experienced in TPE cases
• Indirect ELISA test to  check the rise in anti-filarial titers
• Surgical treatments can be employed to improve drainage in cases of lymphoedema
• Serology³ 

Treatment options

In Acanthocheilonemiasis, antiparasitic drugs and surgery are quite effective.⁴

To eliminate parasitic eggs and larvae, it is recommended to use Ivermectin or diethylcarbamazine (DEC) which reduces the number of worms associated with the symptoms of the disease.³

Monitoring

Is there a need to understand systemic complications arising from this disease?

Yes, because the parasite stays in the body and evades the body’s defence mechanism, which goes on to cause the above problems.

If you suspect you have the mentioned symptoms or experience complications, especially after visiting an endemic zone, it is advisable to contact your physician immediately and inform about your travel history to help with the diagnostics.

Summary 

Acathocheilonemiasis is a very rare parasitic infection and is mostly found in endemic zones. However, its symptoms and complications are similar to other filarial nematodes, thus not leaving us clueless about its identification and management.