A 31-year-old man in Hanoi was very surprised to experience several episodes of swelling in the left scrotum, which became large, itchy, raised, and painful. The lesions gradually moved up to the area below the navel and to the left side of the abdomen, which was quite unusual.
Strangely, every 3-4 days, he noticed the lesions gradually moving up the skin below the navel and to the left abdominal wall with similar symptoms.
Unable to bear it any longer, after three days, he visited Đặng Văn Ngữ Hospital for a check-up, where he received a preliminary diagnosis of subcutaneous larva migrans due to a parasitic infection.
Upon taking his medical history, he mentioned that he really enjoyed eating grilled frog legs. The patient exhibited typical clinical symptoms, a dietary history, elevated eosinophils, and positive serology for Gnathostomiasis.
The lesion moved to the navel area and then to the left abdominal wall. (Photo: BVCC)
The doctor prescribed Albendazole 400mg for him to take over 21 days. By the eighth day, the lesion on the left abdominal wall localized, with reduced itching, less pain, and the swelling gradually subsided. Notably, he even managed to capture a specimen suspected of being a parasite from the lesion site.
Parasitic specimen captured from the lesion site.
Recently, Đặng Văn Ngữ Hospital, part of the Central Institute of Malariology, Parasitology, and Entomology, has also received several patients infected with Gnathostoma, presenting with symptoms of itching and urticaria. All patients had previously visited various dermatology clinics without finding a cause.
Gnathostomiasis in humans is caused by several species of parasitic roundworms, similar to Gnathostoma, which are characterized by their spines, hence the name “spiny-headed worms.”
Infected individuals often consume raw or undercooked meat from freshwater fish, eels, frogs, birds, and reptiles (such as snakes), as well as cyclops (a type of zooplankton, also known as water boatmen) that contain third-stage larvae of Gnathostoma spp.
Recent research by Assoc. Prof. Dr. Nguyễn Văn Chương from the Institute of Malariology, Parasitology, and Entomology in Quy Nhơn and colleagues shows that the rate of people consuming undercooked seafood in the surveyed area is high. Specifically, 16% of residents in Bình Định consume undercooked eel, while the rates for clams and oysters are 6.9%, and for snakehead fish, it is 3.2%. In Quảng Ngãi, the corresponding rates are 13.2%, 6.9%, and 3.2%.
According to Assoc. Prof. Chương, there is a significant correlation between consuming undercooked eel and Gnathostoma infection in humans. The risk of Gnathostoma infection is five times higher for those who eat undercooked eel compared to those who do not.
Symptoms of infection may appear up to 10 years after being infected with Gnathostoma larvae
Two to four weeks after infection with Gnathostoma larvae, patients may exhibit symptoms such as fever, fatigue, poor appetite, nausea, vomiting, diarrhea, and vague abdominal pain.
Swollen areas or lumps under the skin typically appear after about 3-4 weeks. However, medicine has recorded cases where symptoms appeared approximately 10 years after infection.
If the larvae migrate to the skin and soft tissues – the most common form, patients may experience skin lesions in the form of nodules, small bumps, or swellings; with symptoms of swelling, heat, redness, and pain.
Due to the movement of the larvae, patients may also experience localized swelling at the lesion site, which is migratory in nature.
Patients may also suffer from itching and urticaria, primarily at the site of the lesion. This leads many patients to mistakenly seek treatment for atopic dermatitis or contact dermatitis.
Gnathostoma larvae can migrate throughout the body, including the upper limbs, lower back, lower limbs, shoulder areas, abdomen, chest, back, and buttocks.
More dangerously, in some cases, the parasites can invade organs such as the liver, eyes, brain, and spinal cord, leading to related symptoms such as vision loss, blindness, nerve pain, paralysis, coma, and potentially death.
To prevent this disease, the Ministry of Health recommends that the public limit their consumption of high-risk foods, avoid eating raw or undercooked seafood (fish, frogs, toads, shrimp); use hygienic water sources, and avoid drinking untreated water that may contain cyclops.
If unusual symptoms occur, such as itching under the skin or abscesses in the liver or brain detected through imaging, one should consider the possibility of a parasitic infection.
