Anisakiasis and Ascariasis: Parasitic Infections

Anisakiasis: A Parasitic Infection from Seafood

Anisakiasis is a parasitic infection caused by the accidental consumption of Anisakis larvae (white) and Pseudoterranova (yellowish-brown-red) in raw fish meat. These are parasitic nematodes (roundworms) with a transversely striated cuticle. They have a terebrant tooth with the opening of the excretory pole (front of the head), a lipless mouth, and an esophagus divided into a long muscular pre-ventricle and a short, oblique one joined to the intestine. They also have three anal glands near the rectum and a spine or mucron at the end of the tail. The definitive host is marine mammals.

Cycle

When sperm whales defecate, unfertilized eggs are removed. These eggs need to form into larvae first. Mature larvae have three stages:

• Born of the egg (L1)
• Larvae swim (L2) and are consumed by crustaceans and plankton (intermediate host)
• This creates a cuticle, and the L2 (infective L3) is eaten. The fish (intermediate host) eats the crustacean with L3, and it stays in the digestive tract of the fish. Humans (accidental hosts) acquire it by eating fish with the larvae.

Gastric Level

Pathology: Inflammatory reaction, granulomas, eosinophilic abscess, and granulomatous disorder around the larva.

Clinical Presentation: Severe pain and upper abdominal oppression, nausea, and vomiting (4-6 hours post-ingestion). Elimination of the larva.

Intestinal Level

Pathology: Abdominal wall edema, eosinophilic infiltration of all layers, bleeding and ulcers in the mucosa, and necrotic granulomatous abscess.

Clinical Presentation: Severe abdominal pain, nausea, fever, diarrhea, and malaise.

Extraintestinal Level

Rare, benign, different locations, abdominal cavity, abdominal wall, mesentery, and peritoneum.

Allergic Level

Allergy post-consumer, even with cooked meat. There is no need for the existence of gastrointestinal parasitism. There may be coexistence of anisakiasis and Anisakis allergy in the same patient.

Immunological Aspects: Three types of antigens have been identified in Anisakis: somatic, excretory-secretory, and the hemoglobin of the parasite (IgE).

Diagnosis

Consumption of fish before, clinical laboratory:

• Endoscopy
• Contrast radiology
• Histological analysis (biopsy)
• Anisakis skin test
• Specific IgE determination

Treatment and Prophylaxis

• Larval removal
• Laparotomy and surgical resection
• Mebendazole and Tiabendazole

Epidemiology: In Chile, there are gastric cases.

Ascariasis: Intestinal Nematode Infection

Ascariasis is an intestinal nematodiasis caused by Ascaris lumbricoides, a parasite in the human small intestine. The male is smaller than the female. Its pathogenic action is expoliatory, consuming part of the host's nutrition. It is spread by eggs. The eggs generated at the beginning are infertile and need environmental conditions to reproduce. They need to pass through the earth.

The female releases fertilized and unfertilized eggs.

• Fertilized egg: Oval, uniform, with a thick wall and albumin curves.
• Unfertilized egg: Irregular, large, with albumin, and an irregular cortex with more pronounced mamelons.
• Decorticated egg: No mammillations, like the two above.

Cycle

The female in the small intestine eliminates eggs without fertilization. Humans eliminate them outdoors via feces. Eggs need a specific temperature, soil, and shade to become fertile in three weeks. The latent form is the infective egg. The larva then enters through the mouth, intestine, stomach, and liver and goes vertically to the lungs. Without a cuticle, it grows and will be drilled into the lungs. The person has breathing problems, also known as Loeffler's Syndrome.

The larva passes through the bronchi, bronchioles, trachea, and epiglottis, causing a cough. It comes out through the mouth (not shown). Some are removed, but a percentage is swallowed and passed again through the abdomen until installation in the small intestine.

Epidemiology

Wide geographical distribution, especially in children. Socio-economic and climatic conditions are important, with a greater percentage in the central area.

Clinical Presentation

Pulmonary Phase Symptoms

From mild to severe bronchitis (Loeffler's Syndrome).

Intestinal Phase Symptoms

• General: Developmental delay, anorexia.
• Allergic: Hives, nasal itching.
• Intestinal: Cramping pain, nausea, vomiting, diarrhea/constipation.
• Nervous: Irritability, poor sleep.
• Complications: Intestinal obstruction (acute abdomen), Ascaris wandering (appendicitis, peritonitis).

Diagnosis

• Adult stage: Adult worms and eggs (stool sample).
• Larval stage: Imaging, symptoms, and epidemiology.

Treatment

Mebendazole, Albendazole. Do not administer to pregnant women.

Prophylaxis

• Individual: Wash hands after playing with dirt, wash fruits and vegetables under a jet of water, and avoid feeding vectors.
• Collective: Environmental sanitation, research and case management, education, and no use of unsanitary drinking water.