Histology Technician

Field description

Histology is an essential component to the art and science of pathology. The histology laboratory contributes a valuable service to help

pathologists provide patient diagnoses. Information gained through microscopic evaluation of tissue slides prepared by histology technicians

allows a pathologist to either identify or dismiss disease. The preparatory steps taken to ensure a quality diagnosis are key to this relationship.

Knowledge of the basic pathologic conditions, skills in the use of precision equipment, and performance of special stains enable histology

technicians to accurately demonstrate the morphology of tissue specimens. Knowledge of biology, chemistry, anatomy, physiology and medical

terminology is essential for the professional histology technician or technologist. In addition, attention to detail, good manual dexterity, and

above all, a concern for patient well-being are imperative characteristics of a good histology technician.

Endoparasites

Protozoan organisms

Common name of

organism or disease

Latin name

(sorted)Body parts affected

Diagnostic

specimenPrevalence

Source/

Transmission

(Reservoir/

Vector)

Acanthamoeba Acanthamoeba eye, brain culture worldwide

contact

lenses cleaned

with tap water

Babesiosis

Babesia B.

divergens, B.

bigemina,B.

equi, B. microfti, B.

duncani

red blood cells

Giemsa-stained

thin blood

smear

New York, Martha's Vineyard,

Nantucket (different species

have worldwide distribution)

tick bites, e.g. Ixodes

scapularis

Balantidiasis Balantidium coli

intestinalmucosa, may

become invasive in

some patients

stool

(diarrhea=ciliat

ed trophozoite;

solid

stool=large cyst

with horseshoe

shaped

nucleus)

ingestion of cyst,

zoonotic infection

acquired from pigs

(feces)

Blastocystosis Blastocystis intestinal direct

microscopy of

stool (PCR, anti

body)

2 - 20% of population [1] eating food

contaminated with

feces from an

infected human or

Common name of

organism or disease

Latin name

(sorted)Body parts affected

Diagnostic

specimenPrevalence

Source/

Transmission

(Reservoir/

Vector)

animal

Coccidia, cryptosporidiosis Cryptosporidium intestines stool widespread

ingestion of oocyst

(sporulated), some

species are zoonotic

(e.g. bovine fecal

contamination)

DientamoebiasisDientamoeba

fragilisintestines stool

up to 10% in industrialized

countries

ingesting water or

food contaminated

with feces

AmoebiasisEntamoeba

histolytica

Intestines (mainly

Large, can go to

extraintestinal sites)

stool (fresh

diarrheic stools

have amoeba,

solid stool has

cyst)

areas with poor sanitation, high

population density and tropical

regions

fecal-oral

transmission of cyst,

not amoeba

Giardiasis Giardia lamblialumen of thesmall

intestinestool widespread

ingestion of cysts in

fecal contaminated

water or food, can be

zoonotic (deer,

beavers)

Isosporiasis Isospora belliepithelial cells ofsmall

intestinesstool

worldwide - less common

thanToxoplasma or Cryptospori

dium

fecal oral route -

ingestion of

sporulated oocyst

Leishmaniasis Leishmania cutaneou

s,mucocutaneous,

or visceral

visual

identification

of lesion or

microscopic

stain with

Leishman's or

Visceral leishmaniasis-

Worldwide; Cutaneous

leishmaniasis - Old

World;Mucocutaneous

leishmaniasis - New World

Phlebotomus Lutzom

yia- bite of several

species of

phlebotomine

sandflies

Common name of

organism or disease

Latin name

(sorted)Body parts affected

Diagnostic

specimenPrevalence

Source/

Transmission

(Reservoir/

Vector)

Giemsa's stain

Primary amoebic

meningoencephalitis(PAM) [2][3]

Naegleria fowleri brain culture rare but deadly

Nasal insufflation of

contaminated warm

fresh water, poorly

chlorinated swimmin

g pools, hot springs,

soil

Malaria

Plasmodium

falciparum (80% of

cases), Plasmodium

vivax,Plasmodium

ovale, Plasmodium

malariae, Plasmodi

um knowlesi

red blood cells, liver Blood filmtropical - 250 million

cases/year

Anopheles mosquito,

bites at night

RhinosporidiosisRhinosporidium

seeberinose,nasopharynx

reservoir water

and soilIndia and Sri Lanka

nasal mucosa came

into contact with

infected material

through bathing in

common ponds

Toxoplasmosis -Parasitic

pneumonia

Toxoplasma gondii eyes, brain, heart, liver blood and PCR widespread - up to one third of

all humans

ingestion of

uncooked/undercook

ed pork/lamb/goat

with

Toxoplasma bradyzoi

tes, ingestion of raw

milk with

Toxoplasm

atachyzoites,

ingestion of

contaminated water

food or soil

withoocysts in cat

feces that is more

Common name of

organism or disease

Latin name

(sorted)Body parts affected

Diagnostic

specimenPrevalence

Source/

Transmission

(Reservoir/

Vector)

than one day old

TrichomoniasisTrichomonas

vaginalis

female urogenital tract

(males asymptomatic)

microscopic

examination of

genital swab

7.4 million Americans

sexually transmitted

infection - only

trophozoite form (no

cyst)

Sleeping sicknessTrypanosoma

brucei

blood lymph and

central nervous systems

microscopic

examination

of chancre fluid

, lymph node

aspirates,

blood, bone

marrow

50,000 to 70,000 people

tsetse fly, day biting

fly of the

genus Glossina

Chagas disease Trypanosoma cruzi

colon, esophagus,

heart, nerves, muscle

and blood

Giemsa stain -

blood

Mexico, Central America, South

America - 16-18 million

Triatoma/Reduviidae

- "Kissing bug" Insect

Vector, feeds at night

Helminths organisms (worms)

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic specimen Prevalence Transmission/Vector

Ancylostomiasis/Hookworm

Ancylostoma

duodenale, Necator

americanus

lungs, small

intestine,

blood

stool

common in

tropical, warm,

moist climates

penetration of skin by L3

larva

Anisakiasis [4] Anisakisallergic

reactionbiopsy incidental host

ingestion of raw fish,

squid, cuttlefish, octopus

Roundworm - Parasitic

pneumonia

Ascaris sp. Ascaris

lumbricoides

Intestines,

liver,

stool common in

tropical and

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic specimen Prevalence Transmission/Vector

appendix,

pancreas,

lungs, Löffler's

syndrome

subtropical

regions

Roundworm -

BaylisascariasisBaylisascaris procyonis

Intestines,

liver, lungs,

brain

rare: North

Americastool from raccoons

Roundworm-lymphatic

filariasis

Brugia malayi, Brugia

timorilymph nodes blood samples

tropical regions

of AsiaArthropods

Tapeworm - Tapeworm

infectionCestoda intestine stool rare

Clonorchiasis

Clonorchis

sinensis; Clonorchis

viverrini

Lancet liver flukeDicrocoelium

dendriticumgall bladder rare ingestion of ants

Dioctophyme renalis

infectionDioctophyme renale

kidneys

(typically the

right)

Urine Rare

Ingestion of

undercooked or raw

freshwater fish

Diphyllobothriasis -

tapewormDiphyllobothrium latum

intestines,

bloodstool (microscope)

Europe, Japan,

Uganda, Peru,

Chile

ingestion of raw fresh

water fish

Guinea worm -

Dracunculiasis

Dracunculus medinensis subcutaneous

tissues,

skin blister/ulcer South Sudan

(eradication

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic specimen Prevalence Transmission/Vector

muscle ongoing)

Echinococcosis - tapeworm

Echinococcus

granulosus, Echinococc

us multilocularis, E.

vogeli, E. oligarthrus

liver, lungs,

kidney, spleen

imaging ofhydatid cysts in the

liver, lungs, kidney and spleen

Mediterranean

countries

as intermediate host,

ingestion of material

contaminated by feces

from a carnivore;

asdefinite host, ingestion

of uncooked meat (offal)

from a herbivore

Echinostoma echinatum small intestine Far Eastingestion of raw fish,

mollusks, snails

Pinworm - Enterobiasis

Enterobius

vermicularis, Enterobius

gregorii

intestines,

anusstool; tape test around anus

widespread;

temperate

regions

Liver fluke - Fasciolosis [5]

Fasciola

hepatica, Fasciola

gigantica

liver, gall

bladderstool

Fasciola

hepatica in

Europe, Africa,

Australia, the

Americas and

Oceania; Fascio

la

gigantica only

in Africa and

Asia, 2.4 million

people infected

by both species

freshwater snails

Fasciolopsiasis - intestinal

fluke [6]Fasciolopsis buski intestines stool or vomitus (microscope)

East Asia - 10

million people

ingestion of infested

water plants or water

(intermediate

host:amphibic snails)

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic specimen Prevalence Transmission/Vector

Gnathostomiasis [7]

Gnathostoma

spinigerum, Gnathosto

ma hispidum

subcutaneous

tissues (under

the skin)

physical examinationrare - Southeast

Asia

ingestion of raw or

undercooked meat (e.g.,

freshwater fish, chicken,

snails, frogs, pigs) or

contaminated water

Hymenolepiasis[8]

Hymenolepis

nana, Hymenolepis

diminuta

ingestion of material

contaminated by flour

beetles, meal worms,

cockroaches

Loa loa filariasis, Calabar

swellingsLoa loa filaria

Connective

tissue, lungs,

eye

blood

(Giemsa,haematoxylin,eosin st

ain)

rain forest of

West Africa -

12-13 million

people

Tabanidae - horse fly,

bites in the day

Mansonelliasis, FilariasisMansonella

streptocerca

subcutaneous

layer of skininsect

Metagonimiasis - intestinal

fluke

Metagonimus

yokogawaistool

Siberia,

Manchuria,

Balkan states,

Israel, Spain

ingestion of undercooked

or salted fish

River blindness

Onchocerca

volvulus, Onchocerciasi

s

skin, eye,

tissuebloodless skin snip

Africa, Yemen,

Central and

South America

near cool, fast

flowing rivers

Simulium/Black fly, bite

during the day

Chinese Liver Fluke

Opisthorchis

viverrini, Opisthorchis

felineus, Clonorchis

sinensis

bile duct

1.5 million

people in

Russia

consuming infected raw,

slightly salted or frozen

fish

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic specimen Prevalence Transmission/Vector

Paragonimiasis, Lung Fluke

Paragonimus

westermani; Paragonim

us

africanus; Paragonimus

caliensis;Paragonimus

kellicotti; Paragonimus

skrjabini; Paragonimus

uterobilateralis

lungs sputum, feces East Asia

ingestion of raw or

undercooked freshwater

crabs crayfishes or other

crustaceans

Schistosomiasis - bilharzia,

bilharziosis or snail fever (all

types)

Schistosoma sp.

Africa,

Caribbean,

eastern South

America, east

Asia, Middle

East - 200

million people

skin exposure to water

contaminated with

infected fresh water

snails

intestinal schistosomiasis Schistosoma mansoni

intestine,

liver, spleen,

lungs, skin

stool

Africa,

Caribbean,

South America,

Asia, Middle

East - 83 million

people

skin exposure to water

contaminated with

infected Biomphalaria fre

sh water snails

urinary schistosomiasisSchistosoma

haematobium

kidney,

bladder,

ureters, lungs,

skin

urineAfrica, Middle

East

skin exposure to water

contaminated with

infected Bulinus sp. snails

Schistosomiasis b

ySchistosoma japonicumSchistosoma japonicum

intestine,

liver, spleen,

lungs, skin

stool

China, East

Asia,

Philippines

skin exposure to water

contaminated with

infected Oncomelania sp.

snails

Asian intestinal

schistosomiasis

Schistosoma mekongi - South East Asia skin exposure to water

contaminated with

infected Neotricula

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic specimen Prevalence Transmission/Vector

aperta - fresh water

snails

SparganosisSpirometra

erinaceieuropaei

ingestion of material

contaminated with

infected dog or cat feces

(humans: dead-end host)

Strongyloidiasis - Parasitic

pneumonia

Strongyloides

stercoralis

Intestines,

lungs, skin

(Larva

currens)

stool, blood skin penetration

Beef tapeworm Taenia saginata Intestines stoolworldwide

distribution

ingestion of undercooked

beef

Pork tapeworm Taenia soliumingestion of undercooked

pork

ToxocariasisToxocara

canis, Toxocara cati

liver, brain,

eyes

(Toxocara

canis -Visceral

larva

migrans, Ocul

ar larva

migrans)

blood, ocular examinationworldwide

distribution

pica, unwashed food

contamined with

Toxocara eggs,

undercooked livers of

chicken

Trichinosis Trichinella

spiralis, Trichinella

britovi,Trichinella

nelsoni, Trichinella

nativa

muscle,

periorbital

region, small

intestine

blood more common

in developing

countries due

to improved

feeding

practices in

developed

ingestion of undercooked

pork

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic specimen Prevalence Transmission/Vector

countries.

Swimmer's itch

Trichobilharzia

regenti, Schistosomatid

ae

skin exposure to

contaminated water

(snails and vertebrates)

Whipworm

Trichuris

trichiura, Trichuris

vulpis

large

intestine,

anus

stool (eggs)common

worldwide

accidental ingestion of

eggs in dry goods such as

beans, rice, and various

grains or soil

contaminated with

human feces

ElephantiasisLymphatic

filariasisWuchereria bancrofti

lymphatic

system

thick blood smears stained

withhematoxylin.

Tropical and

subtropicalmosquito, bites at night

[edit]Other organisms

Common

name of

organism or

disease

Latin name (sorted)Body parts

affected

Diagnostic

specimenPrevalence Transmission/Vector

parasitic worm Archiacanthocephala

Halzoun

SyndromeLinguatula serrata nasopharynx

physical

examinationMid East

ingestion of raw or undercooked

lymph nodes (e.g., meat from

infected camels and buffalos)

MyiasisOestroidea, Calliphorida

e,Sarcophagidae

dead or living

tissue

Common

name of

organism or

disease

Latin name (sorted)Body parts

affected

Diagnostic

specimenPrevalence Transmission/Vector

Chigoe flea Tunga penetransSubcutaneous

tissue

physical

examination

Central and

South America

Human Botfly Dermatobia hominisSubcutaneous

tissue

physical

examination

Central and

South AmericaMosquitoes and biting flies

Ectoparasites

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic

specimenPrevalence Transmission/Vector

BedbugCimicidae Cimex

lectulariusskin visual Worldwide sharing of clothing and bedding

Head louse - Pediculosis Pediculus humanus hair folliclesvisual identification

under magnificationCommon worldwide head-to-head contact

Body louse - PediculosisPediculus humanus

corporis

visual identification

under magnification

(Vagabond's

disease)

Worldwide

skin-to-skin contact such as

sexual activity and via sharing

clothing or bedding

Crab louse - Pediculosis Phthirus pubispubic area,

eyelashes

visual identification

under magnificationWorldwide

skin-to-skin contact such as

sexual activity and via sharing

clothing or bedding

Demodex - DemodicosisDemodex

folliculorum/brevis/canis

eyebrow,

eyelashes

Microscopy of

eyelash or eyebrow

hair follicle

Pandemic,

worldwideprolonged skin-to-skin contact

Scabies Sarcoptes scabiei skin microscopy of Worldwide skin-to-skin contact such as

Common name of

organism or diseaseLatin name (sorted)

Body

parts

affected

Diagnostic

specimenPrevalence Transmission/Vector

surface scrapingssexual activity and via sharing

clothing or bedding

Screwworm, Cochliomyia Cochliomyia hominivoraxskin and

woundsvisual

North America

(eradicated),

Central America,

North Africa

direct contact with fly

Flea, Siphonaptera Pulex irritans skinvisual identification

under magnificationWorldwide environment

Parasite life cycles can take a variety of forms, all involving the exploitation of one or more hosts. Those that must

infect more than one host species to complete their life cycles are said to have complex or indirect life cycles, while

those that infect a single species have direct life cycles.

If a parasite has to infect a given host in order to complete its life cycle, then it is said to be an obligate parasite of

that host; sometimes, infection is facultative—the parasite can survive and complete its life cycle without infecting

that particular host species. Parasites sometimes infect hosts in which they cannot complete their life cycles; these

are accidental hosts.

A host in which parasites have sexual reproduction is known as the definitive, final or primary host.

In intermediate hosts, parasites either do not reproduce or do so asexually, but the parasite always develops to a

new stage in this type of host. In some cases a parasite will infect a host, but not undergo any development, these

hosts are known as paratenic[1] or transport hosts. The paratenic host can be useful in making it more likely that the

parasite will be transmitted to the definitive host. For example the cat lungworm (Aelurostrongylus abstrusus) uses a

slug or snail as an intermediate host; the first stage larva enters the mollusk and develops to the third stage larva,

which is infectious to the definitive host—the cat. If a mouse eats the slug, the third stage larva will enter the mouse's

tissues, but will not undergo any development.

Parasitic Nutrition is a mode of heterotrophic nutrition where an organism (known as a parasite) lives on the body

surface or inside the body of another type of organism (known as a host). The parasite obtains nutrition directly from

the body of the host. Since these parasites derive their nourishment from their host, this symbiotic interaction is often

described as harmful to the host. Parasites are dependent on their host for survival, since the host provides nutrition

and protection. As a result of this dependence, parasites have considerable modifications to optimise parasitic

nutrition and therefore their survival.

Parasites are divided into two groups: endoparasites and ectoparasites. Endoparasites are parasites that live inside

the body of the host, whereas ectoparasites are parasites that live on the outer surface of the host and generally

attach themselves during feeding[1]. Due to the different strategies of endoparasites and ectoparasites they require

different adaptations in order to acquire nutrients from their host.

Parasites require nutrients to carry out essential functions including reproduction and growth. Essentially, the

nutrients required from the host are carbohydrates, amino acids and lipids. Carbohydrates are utilised to generate

energy, whilst amino acids and fatty acids are involved in the synthesis of macromolecules and the production of

eggs[2]. Most parasites are heterotrophs, so they therefore are unable to synthesise their own 'food' i.e. organic

compounds and must acquire these from their host.

Endoparasitism

Endoparasites are parasites which live inside the body of the host. This group

includes helminths, trematodes and cestodes. Endoparasites are two groups of parasites: intercellular

and intracellular parasites. Intercellular parasites live in spaces within the host e.g. the alimentary canal, whereas

intracellular parasites live in cells within the host e.g. erythrocytes. Intracellular parasites typically rely on a third

organism, a vector, to transmit the parasite between hosts[3][1]. Rather than requiring adaptations to penetrate the

host, as ectoparasites do, endoparasites are in a nutrient-rich location so they instead have adaptations to maximise

nutrient absorption. Endoparasites have a readily available and renewable supply of nutrients inside the host, which

in some cases is pre-digested by the host, so mechanisms of nutrient absorption across their body surface is a

common feature[1]. As part of their life cycle strategy, endoparasites must also be able to transmit from within the host

body and survive the hostile environment within the host. Only by achieving this can they benefit from acquiring

nutrition in this way.

Microvilli structure which increases the surface area available for nutrient uptake in endoparasites

Endoparasites have various anatomical and biochemical adaptations, typically at the host-parasite interface, to

maximise nutrient acquisition. One such adaptation is the tegument, a metabolically active external cover which plays

an important role in the acquisition of nutrients from the host[2]. The parasite tegument is permeable to various organic

solutes and has transporters for the facilitated or active uptake of nutrients. Various studies have attempted to

characterise these transporters in a number of parasites e.g. the amino acid transporter molecules in protozoa [2][4][5].

Cestodes do not have a gut so the tegument is therefore critical for nutrient uptake. In cestodes the tegument is

highly efficient with spine-like microtriches, similar to microvilli, to increase the surface area available for nutrient

acquisition[6]. In many parasites the tegument structure has folds or microvilli to maximise the surface area available

for diffusion and uptake of nutrients. The tegument also commonly has additional organelles and features with

important functions in metabolism including the glycocalyx. The glycocalyx is a carbohydrate-rich layer which

enhances nutrient absorption and secretes enzymes to aid primary digestion[7].

Another important adaptation of endoparasites is the gut, which digests host macromolecules into soluble utilisable

products[2]. This feature is particularly important in endoparasites which are not located in the alimentary canal and

therefore the supply of nutrients is not pre-digested by the host. The gut lining typically has a layer of endodermal

cells which secrete proteolytic enzymes to aid digestion. Some endoparasites have both a gut and anus, some lack

an anus and some have neither i.e. those residing in the alimentary canal which instead diffuse pre-digested host

nutrients across their body surface[2].

The relative importance of the tegument, gut and other adaptations involved in nutrient acquisition varies between

different endoparasitic species.

Tapeworms

Head of the pork tapeworm, Taenia solium ., with attachment structures to attach to the wall of the small intestine

Tapeworms are endoparasites which have numerous adaptations to enhance parasitic nutrition. Tapeworms live in

the small intestine of humans, providing an ideal location to access a readily available, rich source of pre-digested

nutrients[8]. Since nutrients in the small intestine are plentiful and pre-digested by the host, tapeworms do not require

a gut and instead have adaptations to maximise nutrient absorption. Tapeworms have a tegument which allows

nutrients to be absorbed directly from the host small intestine by diffusion. They also have anatomical adaptations in

the form of a scolex with hookers and suckers to allow the parasite to attach to the host small intestine wall,

preventing the tapeworm from being egested following peristalsis [2] . Tapeworms have a flattened body

with microtriches to maximise the surface area available for nutrient absorption and they additionally have various

transporter molecules. Tapeworms have to compete with the host epithelium for nutrients, so it is essential that they

compete more efficiently for nutrients. They also secrete enzymes to enhance host digestive enzymes e.g. pancreatic

α-amylase[2].

Schistosomes

Schistosomes, another type of endoparasite, also live inside the body of the host but instead these parasites acquire

their nutrients from host blood. Schistosomes are in direct contact with host blood, a rich source of amino acids, and

they therefore do not require penetrative structures to reach host nutrients. Schistosomes take blood up through the

negative pressure created by muscle contractions of their sucker and oesophagus[2]. They obtain amino acids from

host blood through a mechanism of haemoglobin degradation, which remains unresolved but is suggested to involve

a series of proteases. Mechanisms to overcome blood clotting are also employed[9][10]. Various studies have

attempted to characterise the components of the schistosome tegument, including transporter molecules suggested

to be involved in nutrient uptake. Such transporter molecules include schistosome alkaline phosphatase (SmAP) and

cathepsin B, which are suggested to be important in nutrient acquisition[11][12][13].

Malaria

Malaria, caused by the apicomplexan parasite Plasmodium falciparum, is an intracellular endoparasite. This parasite

relies on a third organism, in the form of an Anopheles mosquito vector. The host blood provides an ideal rich source

of glucose and amino acids to the parasite, particularly during blood stage infection

where Plasmodium infects erythrocytes [14] . In order to acquire essential nutrients Plasmodiumhas to compete with

both the vertebrate and insect host and therefore must be highly efficient, regulating uptake according to nutrient

availability[14]. Plasmodium, along with many other endoparasitic parasites, have numerous channels in their

parasitophorous vacuole membrane rendering it permeable to organic solutes to allow the uptake of necessary

nutrients. The Plasmodium falciparum hexose transporter (PfHT) is such a transporter, which is critical for the uptake

of glucose and fructose and therefore survival of the parasite[15]. These organic molecules have to cross three

membranes altogether; the plasma membrane of the erythrocyte, the parasitophorous vacuole membrane and

the Plasmodium plasma membrane, facilitated by transporters such as PfHT[16].

Ectoparasitism

Ectoparasites live on the outer surface of the host. This group includes ticks, leeches, mites and the tsetse fly.

Ectoparasites do not have a readily available source of nutrients available on the outer surface of the host so they

therefore require adaptations which enable them to gain access to host nutrients. This requires penetrative features

which can insert into the host, as well as the ability to secrete digestive enzymes and the presence of a gut to digest

host-derived nutrients[1]. Ectoparasites also have a variety of parasite transporters and permeases to enable them to

acquire nutrition from their host, across numerous membranes. Many ectoparasites are known to be vectors of

pathogens, so they therefore transmit these pathogens during nutrient acquisition[17].

Tsetse flies, the insect vector of Trypanosoma brucei, the causative agent of African trypanosomiasis are an example

of an ectoparasite. These insects have specialised structures, known as a proboscis to pierce and draw nutrients

from their host. These then employ transport proteins to transport the essential nutrients across membranes,

ultimately from the host to the tsetse fly gut for digestion. Various permeases have been characterised including

those that import hexoses, carboxylates, and amino acids[18][19].

Another endoparasite is scabies, caused by Sarcoptes scabiei. Scabies, transmitted by female mites, depends on

nutrition from its host for survival. This endoparasite obtains nutrients by burrowing into the skin of the host. Studies

have also identified the presence of scabies mite inactivated protease paralogues (SMIPPs), which are believed to

compete with host proteases[20].

Effects on the host

As mentioned previously, parasitic nutrition is beneficial to the parasite but typically detrimental to the host since it

deprives the host of nutrients. This mode of nutrition has numerous side effects on the host including weight loss,

anaemia, obstruction of the intestine, damage to the host intestinal wall and in some cases transmission of serious

pathogens e.g. the ectoparasitic tsetse fly which transmits African trypanosomiasis[1][14][2][21].

Applications

Nutrient acquisition is an important component of parasite pathogenesis since it is critical to parasite survival [14].

Understanding the mechanisms of parasite nutrient acquisition therefore identifies novel targets which we can exploit

as a form of parasite control e.g. through knock-out or inhibition of crucial transporters or destruction of penetrative

anatomical features. Several studies have looked into nutrient acquisition as a method of parasite control, including

the development of vaccines against helminth parasites by targeting digestive proteases[22].

Parasitic nutrition in plants

Plants are typically autotrophic organisms meaning that they synthesise their own 'food' from inorganic compounds

by photosynthesis. Some plants however are unable to synthesise their own 'food' by photosynthesis and therefore

acquire nutrients by parasitic nutrition from other living plants. Plants which acquire their nutrients in this way are

known as parasitic plants [23] . These plants have modified root structures known as haustorium, which the parasitic

plants use to penetrate the vascular bundle of host plants and essentially 'steal' nutrients from host plants [24][1].

Parasitic plants include Dodder, Rafflesia and Broomrape.