Parasitic infections are typically managed with anthelmintic medications designed to kill or expel the causative organism. These drug therapies are highly effective for most infections where parasites reside within the intestinal tract or circulate freely in the bloodstream. However, certain parasitic diseases present complex pathologies that render drug treatment insufficient or impossible. In these specific cases, surgical treatment is required for either the direct removal of the parasite or the repair of the serious damage it has inflicted.
Why Surgical Intervention is Required
Surgery is necessary when the parasite’s location or its physical effect prevents pharmacological cure or causes immediate danger. One reason is the failure of drug therapy to penetrate certain anatomical locations effectively. For instance, the central nervous system or areas shielded by a fibrous cyst wall often prevent anthelmintic agents from reaching therapeutic concentrations.
Another factor is the formation of a large, space-occupying lesion, such as a cyst or abscess, which poses a mechanical risk. These lesions can compress vital organs, obstruct fluid flow, or threaten rupture, demanding immediate physical removal. Acute obstruction caused by the sheer volume or migration of parasites must also be relieved emergently. In these cases, the therapeutic goal shifts from killing the parasite to physically resolving the mechanical or mass effect.
Infections Requiring Mass or Cyst Removal
Surgical removal is the definitive treatment when a parasite forms a contained, tumor-like structure that cannot be dissolved or safely left in place. Hydatid disease, caused by the larval form of the tapeworm Echinococcus granulosus, is a prime example. Fluid-filled cysts can grow significantly in the liver or lungs, causing symptoms through mass effect, such as compressing adjacent organs or blood vessels. Rupture can be spontaneous or occur during trauma.
The greatest perioperative hazard during removal is the risk of anaphylactic shock. The cyst fluid is highly antigenic, and spillage can trigger a severe, sometimes fatal, hypersensitivity reaction. Surgeons must use meticulous techniques to aspirate the fluid and sterilize the cyst cavity with scolicidal agents before removing the cyst wall, preventing leakage.
Neurocysticercosis, caused by the larval stage of the pork tapeworm Taenia solium, frequently requires surgical intervention when it affects the brain’s ventricles. Cysts lodged here can obstruct the flow of cerebrospinal fluid (CSF), leading to hydrocephalus and increased intracranial pressure. The preferred treatment for accessible intraventricular cysts is minimally invasive endoscopic surgery for direct removal.
If hydrocephalus cannot be managed by cyst removal alone, or if inflammation causes permanent CSF pathway obstruction, a ventriculoperitoneal shunt (VPS) is necessary. This shunt diverts excess CSF to the abdominal cavity, relieving pressure on the brain and managing the mechanical complication.
Interventions for Obstruction and Migration
Acute mechanical obstruction caused by the physical presence or migration of adult worms necessitates prompt surgical action. Ascaris lumbricoides, a large roundworm, can reproduce in high numbers, forming a tangled mass known as a worm bolus that physically blocks the intestinal lumen. This causes small bowel obstruction, a medical emergency that can result in bowel perforation or gangrene.
If conservative management fails, surgery is required to physically remove the bolus, often through an enterotomy. Ascaris worms can also migrate into the biliary tract, causing obstructive jaundice or cholangitis that may require endoscopic or surgical access to clear the bile ducts.
A different intervention is required for Dracunculus medinensis, or Guinea worm, for which no effective drug exists. The adult female worm, which can be up to a meter long, must be slowly extracted from the skin over days or weeks by winding it around a small stick. Surgical intervention is required if the worm breaks during this process, causing a severe inflammatory reaction, abscess formation, and secondary bacterial infection. This requires incision and drainage by medical personnel.
The African eye worm, Loa loa, occasionally requires surgical removal when seen moving across the subconjunctival space of the eye. Surgical extraction is performed as a minor procedure using local anesthesia to immobilize the worm before removal through a small incision.
Surgical Repair of Chronic Damage
Some parasites cause structural damage that persists long after the active infection is cleared, requiring reconstructive or palliative surgery. Schistosomiasis, caused by the blood fluke Schistosoma, is a chronic disease where parasite eggs lodge in tissues like the liver, bladder, and intestines. The immune reaction to these eggs forms granulomas, leading to extensive scarring and fibrosis.
In the liver, this scarring causes severe portal hypertension, which leads to esophageal varices prone to catastrophic bleeding. Surgical procedures, such as shunting operations, reroute blood flow to reduce pressure in the portal system and prevent fatal hemorrhage. Granulomas in the urinary tract can also cause fibrotic strictures, requiring reconstructive urological surgery to restore proper urine flow.
Chronic filariasis, caused by the filarial roundworm Wuchereria bancrofti, causes long-term damage to the lymphatic system. The worms inhabit the lymphatic vessels, causing inflammation and chronic blockages that result in lymphedema, a severe swelling of the limbs. In men, this often manifests as hydrocele, a collection of fluid around the testes. Surgical management includes hydrocelectomy to remove the fluid sac and reconstructive or debulking surgery for severe lymphedema.