Introduction

Histopathology represents a science on structureand function of tissues in ill individuals.Histopathological analysis plays an important rolein the diagnosis of human and animal diseases ofdifferent etiologies such as infectious, neoplastic,parasitic, deficiency diseases and of intoxications.In many cases, parasitic diseases are not properlyrecognized. A cursory diagnosis often leads toprolonged or even ineffective treatment. Histo -patho logical examination of organs or tissuesfacilitates a thorough and accurate diagnosis. Veryoften, histopathological examination allows toidentify the parasite species involved, the area ofpathological lesions, possible complications ofbacterial or viral origin, and the outlook oftreatment. Histopathological examination providesinsight into interactions between pathogens andtheir impact on the host organism [1–3]. Detectionof histopathological changes during certain parasiticinvasions is particularly important for differentialdiagnosis and often confirms the presence ofparasitic diseases.

This study was aimed at determining the role ofhistopathology in the diagnosis of animal parasiticdiseases and revealing pathological changesoccurring during invasions caused by different

parasite taxa: the Protozoa, Trematoda, Cestoda,Nematoda, Acari and Insecta.

Materials and Methods

Tissue samples were collected from variousanimal species (turkey, chickens, reptiles, rabbits,pigs, wild boars, fish and dogs) suspected ofcarrying a parasitic invasion. The materials hadbeen collected for many years and kept asdemonstration specimens at classes of veterinarymedicine at the Division of Parasitology. Thematerials obtained were fixed in 8% formalin.Histological tissue samples were stained withhaematoxylin and eosin (H-E).

Results and Discussion

Most common histopathological changes caused

by protozoans

The histopathological analysis of the largeintestines and livers of turkeys infected revealednumerous oval or circular protozoan parasites withgranular endoplasm, representing Histomonasmeleagridis (Fig. 1). Histopathological examinationof the large intestine and liver of reptiles revealedthe presence of Entamoeba invadens. These

Annals of Parasitology 2014, 60(2) 127–131 Copyright© 2014 Polish Parasitological Society

Original papers

Histopathological diagnosis in parasitic diseases

Zenon Sołtysiak1, Jerzy Rokicki2, Magdalena Kantyka1

1Division of Parasitology, Faculty of Veterinary Medicine, Wrocław University of Environmental and Life Sciences,Norwida 31, 50-375 Wrocław, Poland2Department of Invertebrate Zoology and Parasitology, University of Gdańsk, Wita Stwosza 59, 80-308 Gdańsk,Poland

Corresponding author: Zenon Sołtysiak; e-mail: zenon.soltysiak@up.wroc.pl

ABSTRACT. Histopathological research is very important in diagnosing human and animal diseases. Detection ofhistopathological changes during certain parasitic invasions is particularly important for differential diagnosis and oftenconfirms the presence of parasitic diseases. Such studies allow also to conclude on the primary cause of the disease.

Key words: histopathological research, parasites, tissue changes

protozoan parasites are oval in shape, their nucleiand karyosomes being well-stained. According toBrener et al. [4], the presence of a parasitic diseasein birds can in many cases be confirmed despite theabsence of clinical signs. The study showed cellularand topographic changes of the liver and caecum inturkeys infected with H. meleagridis, thusconfirming the pattern of the hepatic and caecalinfections by H. meleagridis in birds.

The cross-sections of the intestinal wall of pigsinfected with Balantidium coli revealed round oroval protozoan parasites with bean-shapedmacronuclei. The protozoans surrounded theinflammatory infiltrate composed of lymphocytes,histiocytes, and eosinophiles (Fig. 2). In coc -cidiosis-affected rabbits, the schizogony andgametogony damaged the biliary epithelium and

produced clinical symptoms. The coccidiaschizogony and gamogony in some rabbit speciesoccur in the small or large intestine producinghistologically detectable inflammatory changes.Thin gamonts of Eimeria necatrix, E. acervulina,E. precox, E. mivati, E. maxima, E. brunetti andE. tenella were visible within the epithelial cells ofthe small and large intestinal mucosa of chickens.The cross-sections of the intermediate host’sskeletal muscles revealed many zoites (Sarcocystisspp.) within sarcocysts (the Miescher cysts) [5,6].

Histopathological changes caused by flatworms

Liver fluke disease of sheep and cattle, andoccasionally other species, most commonly is due tothe juvenile Fasciola hepatica fluke injures thehepatic parenchyma when moving to the bile ducts.Migration of immature flukes through the liverproduces hemorrhagic tracts of necrotic liverparenchyma. These tracts are grossy visible and inacute infestation, are dark red, but with time becomepaler than the surrounding parenchyma. Repairprocess is often by fibrosis. The Schistosoma

haematobium fluke eggs use their spine to penetratethe wall of the urinary bladder and enter the externalenvironment with the host’s urine. The Schistosomamansoni fluke eggs break through the wall of thecolon into the gastrointestinal tract and in doing sodamage the lamina and mucosa of the largeintestine. The masses of eggs become surrounded byinflamed areas infiltrated by leucocytes, particularlyeosinophiles, in internal organs such as the liver(Fig. 3).

The larval form of Taenia pisiformis burrowstunnels through the hepatic parenchyma of rabbits,

Fig. 1. Histomonas meleagridis – the histologicalstructures of liver are damaged, numerous oval orcircular protozoan parasites with granular endoplasm aresurrounded by the inflammatory cells. H-E, mag. 100x.

Fig. 2. The large intestine of pigs infected withBalantidium coli revealed round or oval protozoanparasites with bean-shaped macronuclei. H-E, mag.100x.

Fig. 3. Eggs of Schistosoma mansoni surrounded byinflammatory cells. H-E, mag.100x.

128 Z. So³tysiak et al.

damaging their liver parenchyma and inducing theformation of a peripheral inflammatory infiltratecomposed of eosinophiles and giant cells. In chroniccases, the damaged liver parenchyma producesfibrotic scars. The second larval form ofMesocestoides spp. is the tetrathyridium found inthe avian and reptilian body cavity, and occasionallyfound in the abdominal cavity of dogs (Fig. 4). Thelarvae of Echinococcus multilocularis s. alveolarisare often located in the liver, lungs or brain. Thelarval forms are surrounded by inflammatoryinfiltration with numerous eosinophiles, necrosisand calcification [6]. The diagnosis is confirmed byhistological detection of Echinococcus larval hooks.

Histopathological changes caused by

roundworms

The Anisakidae nematodes living in marine fishand mammals from the northern and southernhemispheres are parasites of veterinary, medical,and economic importance. Adults of most of themdwell in the alimentary tract of marine vertebratehosts (cetaceans and pinnipeds). The Delphinidaeare the main final host of Anisakis spp. Adults ofPseudoterranova decipiens (sensu lato) andContracaecum osculatum (sensu lato) are foundmainly in the Otariidae and Phocidae [7,8].Histological examination showed L4 and adultparasites attached to the gastric wall. The anteriorparts of anisakids attached to the gastric mucosa andsubmucosa were ruptured and were also associatedwith ulceration. A mucosa surrounding the anisakidsrevealed the presence of more or less confluent focalnecrotic areas. Most small petechial haemorrhageswere located in the gastric wall mucosa and weresurrounded by inflammatory mononuclear cells

such as lymphocytes, histiocytes, eosinophiles andfibroblasts. The necrotic areas showed, located intheir centres, single or multiple parasitic elements ofirregular shape, with a thick segmented cuticlecovering the dorsal and ventral musculature; thelateral, dorsal and ventral chords were observed.Inside the pseudocoel, the elements resemblinggastroenteric-like structures and lateral chords ofthe parasite were detected. The worms provoked asurrounding granulomatous reaction, containing acentral core of necrotic and cellular debris and alarge number of eosinophiles. The lesions exhibitedan inflammatory response of the lamina mucosa andsubmucosa, but did not reach the gastric muscularis.The gastric glands near the parasite attachment weredamaged. The Anisakidae larvae penetrated deepinto the stomach wall and induced haemorrhagesand eosinophile infiltrations causing atrophy andsometimes formation of small cysts, leading to theformation of tissue scars with multiple fibroblasts.Necrotic foci were sometimes calcified.

The lungs of wild boars were damaged by theMetastrongylus spp. Houszka [9] demonstrated theprevalence occurring in wild boars in Poland anopen environment oscillates between 50–89% andup to 100%. The death of 14 young boars in theearly spring of 2000 is given as an example whereextensive metastrongylosis with consecutivepneumonia was diagnosed.

The wild boar lungs examined were focallycongested, dense in consistence; the alteredpulmonary parenchyma in a water test was airless.Parasitic changes in the lungs were present in all thewild boars examined. Dark red lobuli weresurrounded by centrilobular emphysema light pinkin colour. The pulmonary pleura in place in thecentrilobular emphysema was slightly elevated. Thechanges affected mainly the lower parts of the mainlobes of both lungs. The enlarged light bronchiolesand bronchi revealed the presence of numerousnematodes in the bronchiolitis mucus. Abundantnematodes in the bronchioli (over 20 nematodes)cause the extending the cross-section of brioncholi.Abundant nematodes in the bronchioli (over 20nematodes) cause the dilatation of the bronchiolilight. The presence of adult nematodes in thebronchial tree, their movements and their excreta aswell as the antigens secreted cause inflammation ofthe bronchial tree, and then inflammation in thetissue and alveoli causing bronchopneumonia.Larvae migrating through the bronchial alveoli alsodamage alveoli the walls and cause lung tissue

Fig. 4. The Tetrathyridium larvae covert by tegument -inside are present the lime glands. H-E, mag.100x.

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inflammation. The larval nematode migration in thepulmonary parenchyma to the bronchi andbronchioles caused changes and trauma leading tothe development of inflammation expressed byinfiltration of inflammatory cells with numerouseosinophiles (Fig. 5). The mechanical damagehealed through scarring, i.e., the formation of theconnective scar tissue involved in the repair processleading to extensive lung fibrosis. In the lungparenchyma was also reported small necrotic foci,that have been calcified. Mobility of nematodes andantigens secreted, their excreta, and the presence ofeggs resulted in chronic bronchitis and bronchiolitiswith eosinophilic cells. Migrations of larvalMetastrongylus nematodes in the lung parenchymacaused catarrhal pneumonia, the secondary purulentinfection being caused by staphylococci(Staphylococcus spp.).

Respiratory tract infections are caused byparasites, bacteria or viruses, and mixed respiratorytract infections are very common. The interaction ofpathogens exacerbates the disease, wherebypathological changes are more complicated [10].

Numerous authors confirmed the usefulness ofhistopathological examination in evaluation of thedisease process. Marruchella et al. [11] demonstratedthat a concurrent porcine circovirus type 2 maytrigger metastrongylosis, which may subsequentlyresult in severe, and sometimes fatal, pulmonarydisease. Histopathological analysis helped to fullydetermine the causes of the disease in the animalsaffected.

Histopathological changes caused by arthropods

In dogs, burrowing mites (Sarcoptes scabiei v.canis) parasitize in the deep layers of the epidermis(stratum granulosum, s. spinosum). The changes arelocated on the head, rump and at the base of the tail.At the beginning of the invasion, the lesions occuras local, limited skin exfoliation which next createsscaly raids. As the disease progresses, the skin isreddened and thickened, and corneous epidermisforms papule.

Demodex canis occupies the hair follicles andsebaceous glands and causes generation of smallnodules with thinned hair, and excessive skindesquamatio. Initially, the changes appear on thehead, then small lesions form larger, clearlydemarcated, red scalp patches extending to the neck,forelegs and the rest of the body. The disease ischronic (Fig. 6).

130 Z. So³tysiak et al.

Fig. 5. Cross-sections of the bronchus surrounded byinflammatory process with Metastrongylus spp. parasiteinside bronchus. H-E, mag.100x.

Fig. 6. Cross-sections of the Demodex canis in the hairfollicle. H-E, mag.100x.

Fig. 7a. The III stage of Gasterophilus intestinalis larvepresent in horse’s non glandular stomach

The presence of Oestrus ovis larvae causesinflammation of the mucous membrane of the nasalcavity and sinus. Occasionally, the larvae maypenetrate the skull bones and enter the cerebralcavity; clinical signs are similar to those caused byTaenia multiceps called the false gid. Changes in themucous membrane of frontal sinus include catarrh,inflammatory cells infiltration and squamousmetaplasia. The points of attachment of L2 and L3larvae of Gasterophilus intestinalis in the glandularand non-glandular stomach of horses are marked bywastages on both the corneous layer and thesquamous mucosa, accompanied by its focalhyperkeratosis (Fig. 7a). The necrosis focus showedbacterial colonies and infiltration of eosinophilesand neutrophiles. The bottom of the wastage in theproper epidermal layer of the mucous membranefeatured diffuse infiltrates of inflammatory cells(Fig. 7b).

Conclusions

Histopathological examination is useful for anumber of reasons: a/ to detect parasites; b/ to revealthe area of tissue damage caused by migrating larvalforms and mature parasites; c/ to apply appropriatetreatment; d/ to explain why certain treatments arenot effective during a parasite invasion (parasitesdamage parenchymal organs causing permanent

organ dysfunction and inducing formation offibrotic scars). Histopathological examinationprovides insights into interactions betweenpathogens and their impacts on the host organism,particularly in poly-etiological infections.

References

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[9] Houszka M. 2001. Metastrongyloza jako czynnikredukcji pogłowia dzików. Medycyna Weterynaryjna57: 638-640.

[10] Czyżewska E., Dors A., Pomorska-Mól M. 2013.Interakcje między patogenami oraz ich wpływ naobraz zmian patologicznych w układzie oddechowymświń. Życie Weterynaryjne 88: 930-933.

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Received 5 March 2014Accepted 28 April 2014

Fig. 7b. Diffuse infiltrates of inflammatory cellsespecially giant cells during Gasterophilus intestinalislarvae infestation. H-E, mag. 400x.

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