LUNG PARASITES

CESTOIDEA Order: Cyclophyllidea

ECHINOCOCCUS GRANULOSUS

Echinococcus granulosus infection has a world-wide distribution with a higher prevalence in South-America (Argentina, Uruguay), Europe (mediterranean bassin), Northern Africa, Middle East, South-Central and East Asia.

Echinococcus granulosus: hydatidosis is caused by the larval stage of E.granulosus. After ingestion of eggs the onchospheres penetrate the intestinal mucosa and reach host organs (mainly liver and lung) where they encyst within a week reaching 1 cm in diameter in about 5 months.

Echinococcus granulosus: the cysts (2 to 30 cm) are constituted by an external acellular cuticule and an inner cellular "germinal" layer (10-25 µ) that produces the brood capsules containing 6-12 protoscolices or single protoscolices. (Germinal layer with a protoscolex).

Echinococcus granulosus: the larvae (scolices) develop from the germinal layer. The protoscolices are at first evaginated and measure 120-220 by 70-120 µ.

Echinococcus granulosus: the mature rotoscolices have 4 suckers and a rostellum with hooklets and can be observed in the hydatid fluid.

Echinococcus granulosus: detail of the rostellum.

Echinococcus granulosus: the protoscolices then become invaginated and measure 90-140 by 70-120 µm.They can transform into daughter cysts. These cysts can proliferate both internally and externally giving exogenous cysts.Spontaneous or surgical rupture of the cyst can originate a secondary hydatidosis.

Echinococcus granulosus: the liver is the most common site of development of cysts (50-75%). Lesions can be detected by CT scan or echography;a septate structure is a characteristic of active cysts. Treatment is based on surgical and/or medical therapy (albendazole)

Echinococcus granulosus: definitive diagnosis is obtained by means of serologic tests (EIA, IHA, CIEP/Western Blot);the last two are confirmatory tests and are useful for the follow-up of treated patients. -Detail of liver lesion, CT-scan with septa.  -Western blot analysis: both Ag5 (55 and 65 Kd)  and AgB (8, 16, 24 Kd) bands are present.

Echinococcus granulosus: pulmonary infection is observed in about 20-30% of patients. Roentgenografic examination shows round mass lesions and CT scan demonstrates the fluid content of the lesion. Serology has a lower sensitivity in extrahepatic hydatidosis.

Echinococcus granulosus: any other organ can be affected:nervous system, heart, bones, spleen eyes, muscles are the most common sites.  Multiple involvement is frequent.Symptoms and signs depend on the size,the site and the pressure of the cyst on host structures. -CT scan of a spleen cyst. -MRI scans of a muscular cyst.

Echinococcus granulosus: medullary hydatidosis is a severe form of the infection.In this case the mechanical pressure of host tissues caused paraplegia.The surgical treatment allowed resolution of symptoms.The infection relapsed and responded partially to medical treatment.

TREMATODA Order: Plagiorchiata

PARAGONIMUS WESTERMANI

Paragonimus westermani infection occurs in Asia (especially in China, Corea,India, Japan, Laos, Philippines, Sri Lanka, Taiwan, Thailand, Viet-Nam), Central-West Africa, South America (Ecuador, Perù, Venezuela).

Paragonimus westermani: eggs measure 80-100 by 40-60 µm,are golden-brown with a thick shell and a prominent operculum. Eggs are recovered from sputum and faeces. (Fresh examination of stool sediment). 

Cross section of lung containing adult Paragonimus westermani.

INCERTAE SEDIS

PNEUMOCYSTIS JIROVECI (P.CARINII) P.jiroveci: the infection has a world-wide distribution and the transmission seems to occur by airborne route.The organims that causes human pneumocystosis is now named Pneumocystis jiroveci * Frenkel 1999,in honor of the Czech parasitologist Otto Jirovec.  The organism is now considered a fungus,based on nucelic acid and biochemical analysis; nevertheless,on the basis of morpholocic and biologic characterisitcs it is included in the atlas of medical parasitology.

Pneumocystosis is one of the most common infections in immunosuppressed patients with AIDS.Other impairements of cellular immunity such as primary immunodeficiencies,steroid treatment, organ transplantation and cancers predispose to P.c. infection. This typical chest roentgenogram shows diffuse bilater interstitial infiltrates from the hilar region.

P.jiroveci: infiltrates are usually diffuse but atypical presentations can occur:nodules, cavitation, consolidation, pneumatocele and pneumotorax.

P.jiroveci: after inhalation the microorganism reaches the alveoli and adheres to the type I pneumocytes.The trophozoites then multiply slowly but extensively in the lungs and progressively fill the alveoli that are finally stuffed by the foamy exudate. The classical exudate consists of clusters of P.jiroveci, degenerated cells,host proteins and few alveolar macrophages.H&E stain.

P.jiroveci: in tissue sections obtained with open lung biopsy or at autopsy the alveolar space appears filled by honeycombed material consisting in clusters of P.jiroveci, host proteins and degenerated cells. A scanty inflammation is present.As the disease progresses interstitial hyperplasia with edema and infiltration occur. H&E stain.

P.jiroveci: clusters of cysts are demonstrated in the alveolar space with stains which are selective for the "parasite" wall: methenamine silver and toluidine blue O. Open lung biopsy, silver methenamine stain.

P. jiroveci: clusters of cysts are demonstrated in the alveolar space P.jiroveci: clusters of cysts are demonstrated in the alveolar space. Open lung biopsy, silver methenamine stain.

P.jiroveci: with higher magnification single cysts are visible within the cluster. Open lung biopsy, silver methenamine stain.

P.jiroveci diagnosis: fiberoptic bronchoscopy with BAL is actually the most commonly used diagnostic procedure. The diagnosis is based on the observation of cysts and trophozoites. Clusters of P.jiroveci can be observed in wet mount preparations.

P.jiroveci: at higher magnification cysts with intracystic bodies can be detected within the clusters. (Wet-mount preparations).

P.jiroveci: empty, collapsed and filled cysts cohexist inside the cluster and can be observed with oil immersion.(Wet-mount preparations)

P.jiroveci: the bronchoalveolar lavage can be stained with specific stains for trophozoites like Giemsa. Clusters of typical pleomorphic trophozoites (1-3 micron) and cysts can be observed: trophic forms appear with reddish nuclei and blue cytoplasm.

P. jiroveci: with Giemsa stain cysts (approx P.jiroveci: with Giemsa stain cysts (approx. 5-8 µm in diameter) are variably stained. Intracystic bodies are present in different numbers within the cysts. Mature cysts have 8 intracystic bodies. Some cysts appear empty.

P.jiroveci: cysts have a thick wall: sometimes the wall appears as a transparent outline with intracystic bodies.

P.jiroveci: the sediment of the BAL can be stained with stains for the cysts wall such as methenamine silver. The cysts are well recognizable as round,oval or flat bodies of approx. 4-5 µm in diameter. Gomori's methenamine silver stain (GMS).

P.jiroveci: fungi have the same affinity for silver methenamine and can be confused with P.jiroveci cysts. Cryptococcus neoformans in a BAL specimen.(GMS stain).

P.jiroveci: toluidine blue O stains the cysts wall as silver methenamine. Clusters of P.jiroveci are composed of cysts in different stage of development (empty, collapsed and mature cysts). Toluidine blue O stain.

P.jiroveci: sometimes with toluidine blue O some clusters appear as honeycombed material containing few cysts. Toluidine blue O stain.

P. jiroveci: crowded and collapsed empty cysts 4 µm in diameter P.jiroveci: crowded and collapsed empty cysts 4 µm in diameter.  Cyst wall is blue. Bronchoalveolar lavage from a patient suffering from AIDS.  Gram-Weigert stain. Objective 100 X

P.jiroveci: indirect immunofluorescence  using monoclonal antibodies, FITC coupled,  is a sensitive and specific technique of diagnosis.

P. jiroveci: with transmission electron microscopy (TEM) clusters of P P.jiroveci: with transmission electron microscopy (TEM) clusters of P.jiroveci appear composed of cysts in different stages of development, of empty, collapsed cysts and of trophozoites. (TEM, 2.200 X).

P.jiroveci: with transmission electron microscopy cysts show a thick wall and the intracystic bodies a nucleus and mitochondria.(TEM, 11.500 X).

P.jiroveci: collapsed cyst within a cluster of P.jiroveci. (TEM, 15.500 X).