Clinical Evidence Of Parasitism

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Parasitology

 

Clinical Evidence Of Parasitism

 

 

 

Few of the signs described below are pathognomonic for parasitic

infection because most are not specific. Some of the signs should

indicate parasitic disease for any complete differential diagnosis

list. This is not a comprehensive listing of all agents that should

be included for any symptom listed, but gives an idea of its

importance. Non-parasitic etiologies are not considered.

 

 

 

 

 

 

 

GENERAL TOXIC MANIFESTATIONS

 

Allergic reaction

 

Skin or respiratory symptoms due to localized patient

response to salivary secretions and venoms (arthropod parasites).

Toxocara canis and T. cati can cause transient allergic problems.

Anaphylactic shock can be the result of ruptured hydatid cysts with

Echinococcus granulosus or E. multilocularis infection.

 

 

 

Diarrhea/dysentery

 

Can accompany the gastrointestinal presence of helminthic

parasites. Trichuris trichiura, Ancylostoma duodenale and Necator

americanus. Also, Taenia saginata, Taenia solium. Schistosoma

mansoni can produce diarrhea with blood and mucous. Clonorchis

sinensis can cause diarrhea, too. Opisthorchis sp. liver fluke

infection and Paragonimus westermanii infection can cause diarrhea.

 

Amebic dysentery is caused by Entamoeba histolytica.

 

 

 

Fever

 

Toxic reactions to parasite presence and metabolites

produces high fever in filarial parasite infections.

 

Schistosoma haematobium produces toxemia characterized by

fever. Also S. mansoni and S. japonicum

 

Paragonimus westermanii infection can cause fever with

night sweats.

 

Trichinella spiralis induces fever in late stages of the

infectious process.

 

Toxoplasma gondii can cause fever early in the infectious

cycle.

 

 

 

Fever with chills

 

Characteristically occurs within 2 weeks in non-immune

patients exposed to vivax or ovale malaria (periodicity: every third

day).

 

Falciparum malaria causes swinging temperature (periodicity:

 

Malariae malaria causes mild illness like vivax but with a

quartan periodicity (every fourth day).

 

Food poisoning (general symptoms suggesting this)

 

Irritation due to excystation and invasion of the duodenum by

Trichinella spiralis can produce symptoms reminescent of food poisoning.

 

 

 

Toxemia

 

Severe toxemia is an end-stage symptom of Trichinella

spiralis infection.

 

 

 

 

 

 

 

GENERALIZED SYSTEMIC SYMPTOMS

 

Anemia

 

Hookworm/whipworm infestation. Mechanical loss of blood,

particularly in poorly nourished patients. (Trichuris trichiura,

Ancylostoma duodenale and Necator americanus). Hookworm infestation

produce microcytic hypochromic anemia as a result of blood loss,

especially with ascariasis (trichuriasis is not as severe).

 

Malaria causes anemia due to RBC destruction during

release of merozoites during erythrocytic schizogony. Severe anemia

is characteristic of falciparum malaria.

 

Trypanosomiasis and some tapeworm infections are also

characterized by anemia. Kala-azar and trypanosomiasis produce anemia

as a consequence of hyperproliferation of infected bone marrow cells.

Schistosomiasis and fasciolopsiasis can induce anemia in part from

nutritional deprivation.

 

 

 

Anorexia

 

Generalized loss of appetite that occurs as a consequence

of infection with several parasitic agents. Hymenolepsis nana and

Clonorchis sinensis are commonly associated with anorexia.

Opisthorchis sp. liver fluke infection can cause anorexia.

 

 

Asthma, bronchial

 

Asthma attacks may occur in Ascaris infection during the migration

stage. Later in the disease, hypersensitization to worm antigen can

precipitate an attack. Visceral larva migrans can also exacerbate

asthma and cause marked eosinophilia.

 

 

 

Cough

 

Caused by Ascaris lumbricoides; more rarely, Ancylostoma duodenale and

Necator americanus). Localization of Toxocara canis or T. cati larvae

to the lungs can produce cough also. Respiratory distress can be a

result of hydatid cyst localization with Echinococcus granulosus or E.

multilocularis infection. Also Paragonimus westermanii infection.

 

 

 

Dysuria (and hematuria)

 

Schistosoma haematobium causes urinary tract problems

including incontinence, dribbling, hematuria, obstruction. Repeated

bacterial UTI.

 

 

Diarrhea

 

Many different parasitic agents cause diarrhea at some point in the

life cycle. Some live their entire lives in the intestinal tract,

giving rise to chronic diarrhea syndromes. Others lay eggs at key

times and this causes diarrhea attacks. Still others cause bowel wall

damage and mechanical irritation that precipitates attacks. A chart

listing the organisms and characteristics is below.

 

 

 

PARASITE

 

 

CHARACTERISTICS

 

 

MECHANISMS

Isospora belli

 

 

Protozoan

 

 

Mild abdominal pain; nausea, vomiting, diarrhea

Cryptosporidium parvum

 

 

Protozoan

 

 

Sm & Lg intestinal brush border epithelium

Cyclospora

 

 

Protozoan

 

 

Acid-fast staining; chronic diarrhea in AIDS patients

Giardia lamblia

 

 

Protozoan

 

 

Malabsorption syndrome with gas & steatorrhea (fatty, pale, sticky,

odorous)

Hymenolepis nana

 

 

Cestode

 

 

Development of cysticercoids in intestinal villi may elicit mucoid

diarrhea

Trichinella spiralis

 

 

Cestode

 

 

Maturation in the duodenum & jejunum walls causes nausea, vomiting,

colic, diarrhea

Strongyloides stercoralis

 

 

Trematode

 

 

Inflammation & scarring; lytic tissue damage during migration

 

 

 

Elephantiasis

 

Blockage of lymphatic vessels by parasites and fibrotic change leads

to gross enlargement of extremities or genitals with filarial

parasites. Wuchereria bancrofti; Brugia malayi are less commonly

associated with this problem.

 

 

 

Eosinophilia

 

Shistosoma haemetobium, S. mamnsoni, S. japonicum,Wuchereria

bancrofti; Brugia malayi

 

 

 

Epididymitis and orchitis (eventually hydrocele)

 

Wuchereria bancrofti; Brugia malayi less commonly. Swelling and gross

enlargement of the affected organ.

 

 

 

Neurological Symptoms

 

Headache can be due to CNS involvement with parasites that localize to

nervous tissue (space occupying lesions: Cysticerci of Taenia

solium). Schistosoma mansoni and S. japonicum infection can also

manifest as CNS symptoms. This is also possible with hydatid cyst

localization in Echinococcus granulosus or E. multilocularis

infection. Paragonimus westermanii infection can also cause CNS symptoms.

 

CNS involvement is common with falciparum malaria, including mental

confusion and coma. Trypanosomiasis usually is accompanied by

headache and malaise. Other CNS signs are irritability, changes in

personality and irresistible sleep.

 

 

 

Irritability

 

Can be due to CNS involvement with parasites that localize to nervous

tissue (space occupying lesions: Cysticerci of Taenia solium).

Hydatid cyst localization with Echinococcus granulosus or E.

multilocularis infection can also produce generalized CNS symptoms.

 

 

 

Lymphangitis

 

Lymph node enlargement. Can be caused by filarial parasitic infection

(Wuchereria bancrofti or Brugia malayi). Toxoplasma gondii infection.

 

 

 

Monocytosis

 

Indicative of visceral leishmaniasis (L. donovani).

 

 

 

Neutrophilic leukocytosis

 

Typical blood change indicating hepatic or extra-intestinal amoebiasis

or bacterial invasion of colonic lesions.

 

 

 

Rashes

 

 

 

 

 

Wasting

 

Generalized " failure to thrive " as a consequence of infection by

several parasitic agents. Malabsorption of nutrients due to adult

intestinal nematodes can be one cause (Ascaris lumbricoides, Trichuris

trichiuraAncylostoma duodenale and Necator americanus). Intestinal

cestodes are another (Taenia saginata, Diphyllobothrium latum,

Hymenolepsis nana). Fasciola hepatica and F. buski are also

associated with this symptom.

 

 

 

Weakness

 

Opisthorchis sp. liver fluke infection can cause weakness

 

 

 

Weight loss

 

Can be caused by many different parasites. Malabsorption of nutrients

due to the presence of adult intestinal nematodes can be one cause

(Ascaris lumbricoides, Ancylostoma duodenale and Necator americanus).

Intestinal cestodes can be another (Taenia saginata, Diphyllobothrium

latum, Hymenolepsis nana). Fasciola hepatica and F. buski are also

associated with this symptom. Trypanosomiasis is associated with

weight loss (T. cruzi, T. brucei gambiense). Also indicative of liver

abscess (Entamoeba histolytica).

 

 

 

SPECIFIC LOCALIZATION REACTIONS

 

 

 

Abdominal Pain

 

Crampy abdominal pain may characterize amebic colitis. Tenesmus may

occur if the mucosal lesions are present in the rectum. Diarrhea or

dysentery-like stools are usually present with the infection is

symptomatic. RUQ Pain is characteristic of hepatic abscess. Pain

with giardiasis is usually mild, but can be severe. Pain is not

usually a problem with wom infestations unless complete obstruction of

the bowel is present. Invasion of the intestinal wall by

Strongyloides stercoralis may be accompanied by ulcer-like pain.

Eosinophila is common for all of these diseases.

 

 

 

Appendicitis

 

Pain, constipation, diarrhoea, anorexia, fever malaise,

dysuria. Ascaris lumbricoides, Trichuris trichiura, Taenia saginata,

and Diphyllobothrium latum can cause appendicitis. Ascaris or

Trichuris worm blockage of the lumen may induce appendicitis.

Surgical intervention is necessary in both cases. Occasionally this

is true for Enterobius vermicularis as well. Amebic ulceration also

may simulate appendicitis.

 

 

 

Arthritis

 

Occasionally arthritis is a problem with Dracunculus

medinensis infection.

 

 

Ascites

 

Tissue fibrosis in response to the presence of Schistosoma mansoni and

S. japonicum eggs released during infection may cause increased portal

hypertension, splenomegaly and ascites accumulation in the abdominal

cavity.

 

 

Blackwater fever: see Hemoglobinuria

 

 

 

Blindness and/or eye disease

 

Localization of Toxocara canis or T. cati larvae can

produce blurred vision and blindness. Ocular onchocerciasis can cause

opacities and photophobia; later keratitis with blindness and

glaucoma. Occasionally migrating worms can be seen beneath the

conjunctiva with Loa loa infection.

 

Orbital edema is a notable symptom with Trichinella

spiralis infection.

 

 

 

Brain localization

Congenital toxoplasmosis (Toxoplasma gondii) may present

as areas of intracerebral calcification in a patient with other signs

like chorioretinitis. These are cysts that have been contained and

surrounded by calcium deposits and characterized as " ring-enhancing

lesions " on imaging studies. Another parasitic disease that produces

such lesions is cysticercosis caused by Taenia solium cyst forms.

 

 

Calabar swellings

 

Sucutaneous swellings seen in Loa loa infection. They itch intensely

(pruritis) and may be very painful where little loose connective

tissue is available. They develop quickly to ~2 cm diameter and

persist for several days.

 

 

Chagoma

 

Hard, reddened, raised lesions caused by Trypanosoma cruzi infection,

these usually develop on the head or neck of the infected individual

and last for two-three months. Should not be confused with Romana's

sign, which is edema also associated with T. cruzi.

 

 

 

Cholecystitis

 

Infection of the gall bladder caused by some parasitic

infections (Ascaris lumbricoides,

 

 

Chorioretinitis

 

Infection of the retina and choroids by Toxplasma or (rarely)

Entamoeba histolytica may produce visual disturbances. The effect can

be extreme if the macula is involved. On ophthalmoscopic examination,

a grayish or yellow-white area surrounded by exudates is seen early.

Healing leaves a white atrophic patch bordered by pigment deposits.

 

 

Chyluria

 

This condition is due to lymphatic fluid draining into the urinary

tract from ruptured varices caused by filarial lymphangitis

(microfilariae). The urine will have a whitish appearance.

 

 

 

Colitis

 

Entamoeba histolytica: Occurs within a few days after the patient

ingests amoebic cysts, if the strain has a high pathogenic index.

 

 

Coma

 

Sudden onset of coma in a healthy person predisposed to malaria

because of travel from an endemic region or in a person known to have

falciparum disease is an emergency situation probably resulting from

cerebral malaria. Coma can also occur with other forms of malaria.

In African typanosomiasis, coma follows meningoencephalitis of

increasing severity. Primary amebic meningoencephalitis is

characterized by a history of rapidly developing fever, meningeal

signs, confusion and coma after swimming (especially diving) in fresh

water. Cerebral cysticercosis may be a diagnostic consideration in

persons of Hispanic origin, or of living in Mexico/South America who

present with neurological symptoms including headache, alteration of

consciousness, focal seizures, coma and internal hydrocephalus.

Serology may be useful.

 

 

Conjunctivitis

 

Chronic conjunctivitis is seen in onchocercal infections.

Hyperpigmentation, photophobia and corneal opacities are common.

 

 

Convulsions

 

Focal convulsive seizures are seen in a number of parasitic

infections. In addition to malarial paroxysm, acute toxoplasmosis in

the newborn and Ascaris infection in children can cause convulsions.

See more under Neuological Symptoms.

 

 

 

Dermatitis

 

Penetration of the foot skin causes transient dermatitis with

concomitant itching in patients who have come into contact with larval

forms of Ancylostoma duodenale and Necator americanus. Toxocara canis

and T. cati can cause transient skin problems, depending upon

localization. A papular rash at the site of penetration is common for

Schistosoma haematobium, S. mansoni, and S. japonicum. Penetration of

schistosome cercariae through the skin causes a localized edema and

pruritus. It is mild with human schistosomes, more profound with bird

schistosome cercariae (common in N. America as " swimmer's itch " ). A

papular rash is also noted for Onchocerca volvulus, with thickening of

the skin, loss of elasticity and depigmentation. The microfilariae in

the skin can elicit an acute pruritic inflammatory reaction resembling

erysipelas. It is usually confined to the face, neck and ears, and

repeated attacks and scratching will cause lichenification and

hyperpigmentation of the skin. Loa loa beneath the skin may be

indicated by a thin raised reddened line up to a few cm in length and

causes subcutaneous swellings. Localized ulceration can be caused by

Dracunculus medinensis, especially on the lower legs when the female

is ready to exit the skin to lay eggs. Blotchy irregular large

macular rash patterns, especially on the trunk are indicative of

trypanosomiasis. Maculopapular rash is also characteristic of early

stages of Trichinella spiralis infection. Stongyloides larvae cause a

similar pruritic reaction when penetrating the skin; hookworm larvae

cause vescicles or papules to form at the site of penetration. The

cutaneous larva migrans reaction caused by larvae of Ancylostoma

braziliense consists of a papule at the site of entry and forms a

serpiginous tunnel with vesicles and later crusts covering it. The

area itches intensely and infection may persist for months without

treatment. Sarcoptes scabiei burrows through the skin, producing

lesions that are similar to cutaneous larva migrans. Disease is

highly infectious.Interdigital, popliteal and inframammary folds and

the groin are favorite sites for the parasite. In Pediculus humanus

infestations some patients will have hypersensitivity reactions,

usually due to repeated exposures. Reddish papules at the louse

feeding sites will form, vesiculate and a weeping dermatitis results.

 

 

 

Leishmania donovani infection (visceral leishmaniasis) has a dermal

manifestation that occurs about a year after treatment of kala-azar.

The lesions may be flattened or derpressed depigmented macules, or

erythematous nodules, with amastigotes found in the lesions. Look for

more information under Rashes.

 

 

 

Filarial Abscess

 

An abscess may appear spontaneously or may start only after treatment

has begun. An abscess will usually appear along the lymphatics or at

the lymph nodes. It will be sterile upon lancing (no pus as with

pyogenic abscess) and fragments of adult worms might appear in the fluid.

 

 

 

Hematuria

 

Schistosoma haematobium can cause bloody urine.

 

 

 

Hemidiaphragm, elevated right

 

When parasite eggs are deposited in the lungs, granulomatous reactions

can induce neovascularization and pulmonary arterial fibrosis. These

can induce pulmonary hypertension and right-sided cardiac failure.

 

 

 

Hemoptysis

 

Bloody sputum caused by Ascaris lumbricoides; more rarely, Ancylostoma

duodenale and Necator americanus). Echinococcus granulosus or E.

multilocularis cause this symptom due to daughter cysts being coughed

up during secondary infection. Also caused by Paragonimus westermanii.

 

 

 

Intestinal obstruction

 

Caused by a large adult worm burden in the intestines. Ascaris

lumbricoides, Taenia saginata).

 

 

 

Intestinal ulceration

 

A symptom produced concomitantly with amoebic colitis.

 

 

 

Liver abscess

 

Liver invasion is characterized by tenderness and enlargement;

progressive malaise; irregular spiking fever with night sweats;

leukocytosis; fixed and elevated right diaphragm; sometimes, right

lower lobe pneumonia. Rupture can cause complications including

empyema, lung abscess, peritonitis, thrombosis.

 

 

 

Liver enlargement with tenderness upon palpation

 

Tenderness due to periportal fibrosis occurs with certain egg-laying

parasites that favor periportal circulation (Schistosoma mansoni).

Larval ascariasis causes liver enlargement, as does Toxocara canis or

T. cati infection. Also Clonorchis sinensis, with cholangitis and

biliary cirrhosis.

 

 

 

Liver failure and ascites production

 

Schistosoma mansoni and S. japonicum

 

 

 

Myalgia

 

Muscle aches and tenderness are characteristic of secondary stage

Trichinella spiralis infection.

 

 

 

Myocarditis

 

Localization of Toxocara canis or T. cati larvae can produce

myocarditis. Late stages of Trichinella spiralis infection can also

produce this problem.

 

 

 

Pancreatiasis

 

Infection of the pancreas caused by some parasitic infections (Ascaris

lumbricoides)

 

 

 

Perianal pruritus

 

Enterobius vermicularis infection causes perianal pruritus, especially

nocturnally.

 

 

 

Pneumonitis/Pneumonia

 

A heavy inoculum of nematode eggs can produce pneumonitis within a few

days. The same organisms listed under hemoptysis cause this, and for

the same reasons. Pneumonitis can be caused by Ascaris lumbricoides;

more rarely, Ancylostoma duodenale and Necator americanus.

Echinococcus granulosus or E. multilocularis cause this symptom due to

daughter cysts being coughed up during secondary infection. Also

caused by Paragonimus westermanii.

 

 

 

Rectal prolapse

 

Can be caused by extreme parasite burden (Trichuris trichiura).

 

 

 

Splenic enlargement

 

Toxocara canis or T. cati infection can produce

enlargement of the spleen.

 

Schistosoma mansoni and S. japonicum. Plasmodium vivax

and P. ovale and Toxoplasma gondii may also cause splenic enlargement.

 

 

 

Subcutaneous nodules

 

Cysticerci of Taenia solium can localize to the skin and

produce urticaria and nodules upon dying. Also seen with Paragonimus

westermanii.

 

 

 

Urticaria

 

Skin sensitivity and itching caused by localization of

Taenia solium cysticerci to the skin.