Paragonimus westermani - Host Immunity, Clinical Manifestation, Complication, Prognosis

Host Immunity of Paragonimus westermani

In parasitic infection by Paragonimus westermani, the host immune response includes an elevated level of specific antibodies in the host serum. However, these circulating antibodies do not give any protection against the infection.

Cell-mediated immunity (CMI) is also induced. It is responsible for delayed hypersensitivity which may persist for several years even after the infection has been cured.

Clinical Manifestations of Paragonimus westermani

The incubation period is between 10 to 12 weeks. In light infections, paragonimiasis is asymptomatic i.e. clinical manifestations of Paragonimus westermani are absent.

Acute paragonimiasis

Symptoms in acute paragonimiasis, which lasts for several weeks, include diarrhea, urticaria, and abdominal pain which is related to the invasion of the intestine and migration of larvae. These clinical manifestations of Paragonimus westermani are followed by fever, cough, chest pain, night sweat, dyspnoea, etc.

Chronic paragonimiasis

In chronic clinical manifestations of Paragonimus westermani, the disease may manifest as pulmonary paragonimiasis or extra-pulmonary paragonimiasis depending upon the area in which the parasite is residing.

Pulmonary paragonimiasis

• a most common form of infections

• common symptoms include night seat, pleurisy pain, cough, rusty or golden brown sputum, recurrent bacterial pneumonia (secondary infection)

• other clinical syndromes, which usually occur 6 months after infection, include eosinophilia, hemoptysis which is aggravated by exercise or intense physical work

• as the disease progresses, other syndromes are observed

  * presence of lung abscess or pleural effusion

  * exudative effusion which contains eosinophils, Charcot-Leyden crystals

  * lesions progress to form cystic fibrosis and eventual calcification in the lungs

• since it mimics pulmonary tuberculosis, confusion or misdiagnosis may occur

Extra-pulmonary paragonimiasis

Extra-pulmonary paragonimiasis is much more severe and occurs due to the migration of Paragonimus westermani larvae or the introduction of eggs into body circulation.

It is of following types:

• Abdominal paragonimiasis

• Cerebral paragonimiasis

• Subcutaneous paragonimiasis

• Miscellaneous paragonimiasis

Abdominal paragonimiasis

• Symptoms of abdominal paragonimiasis include abdominal mass, abdominal pain, muco-sanguineous diarrhea

Cerebral paragonimiasis

• cerebral paragonimiasis clinically resembles cerebral cysticercosis

• clinical manifestations include convulsions, jacksonian epilepsy, cephalgia, hemiplegia, paresis, and visual disorders such as optic atrophy, papilloedema

• is rare - occurs in less than 1% of symptomatic cases

Subcutaneous paragonimiasis

• subcutaneous paragonimiasis includes the presence of swelling or subcutaneous nodules- found in the inguinal region as well as the lower abdomen

• these nodules are tender, firm, and mobile which can contain developing Paragonimus westermani

Miscellaneous paragonimiasis

• miscellaneous paragonimiasis of extra-pulmonary paragonimiasis includes various sites where Paragonimus westermani may be present

• includes liver, spleen, kidney, testes, ovary, mesenteric lymph nodes

Complications of Paragonimus westermani

Complications of Paragonimus westermani in pulmonary paragonimiasis are lung abscess, pleural effusion, and empyema.

Complications of Paragonimus westermani in cerebral paragonimiasis are seizures and coma.

Prognosis of Paragonimus westermani

If acute paragonimiasis is left untreated, death may occur.

For pulmonary paragonimiasis, specific treatment is required. Within a few weeks of treatment, eggs from sputum and clinical syndromes associated with the condition are resolved.

In cerebral paragonimiasis, the prognosis is poor with a mortality rate of 5% in untreated cases.

The prognosis of Paragonimus westermani for miscellaneous paragonimiasis is also bad.