JVMM NOTES | PARASITOLOGY| INTRODUCTION & TECHNIQUES IN PARASITOLOGY

UST FMS 2016 | SECOND SEMESTER, 2013-2014 |joelvergilmmendiola@yahoo.com 1

INTRODUCTION TO PARASITOLOGY November 2013 Lecturer: Dr. Borromeo

Parasite

general types: 1. facultative 2. obligate

life cycle: 1. simplex 2. complex

Host

reservoir - maintains parasite

essential reservoir - cats in toxoplasmosis

intermediate - asexual stage

definitive - adult; sexual stage Vectors

biological - both vector and host - Ex Anopheles

mechanical - transmits parasite only - Ex flies in Trachoma

Important Groups of Animal Parasites I. Sarcomastigophora

a. Sarcodina = Amoeba b. Mastigophora = Flagellates

II. Apicomplexa (Sporozoa) = tissue parasites a. Plasmodia = blood b. Isospora, Cyclospora, Cryptosporidium, Sarcocystis

= GIT c. Toxoplasma (and Sarcocystis) = organs and tissues

III. Microspora = Microsporidia (intracellular parasites) IV. Ciliospora = ciliates V. Platyhelminthes = Flatworms, Trematodes and Cestodes VI. Aschelhelminthes = Nematodes VII. Acanthocephala = thorny headed worms; endoparasites VIII. Anthropoda IX. Pentastomida = tongue worms Adaptations to Parasitism

1. absence of locomotor organelles = parasitic protozoa 2. absence of cilia = trematodes and cestodes 3. reduced or absence of GIT = flatworms 4. highly developed reproductive tract = flatworms 5. specialized suckers and hooks 6. larger size than free living 7. streamlining or loss of biochemical pathways =

Leishmania and Entamoeba histolytica 8. mechanisms affecting entrance into host = E. histolytica

has proteolytic enzymes; Hymenolepis nana embryo has hooklets

Effects of the Parasite on the Host

1. interference of the vital processes of the host - Diphyllobotrium latum = megaloblastic anemia - Fasciolopsis buski = toxemia

2. invasion/destruction - Entamoeba histolytica = ulcers - Malaria = RBC destruction - Ascariasis = perforation

3. immunosuppression = Schistosoma 4. host-like antigens and antigenic variation = escape from

immune-mediated response 5. secretions and excretions of protozoa and helminthes =

stimulates host resistance

Effects of the Host on the Parasite

1. Duffy blood group = negativity confers resistance to P. vivax ; seen among Africans

2. SS Trait = increased resistance to P. falciparum 3. high-protein diet = unfavorable to amoebas 4. carbohydrate-rich diet = favorable to tapeworms 5. immunity

a. only to a limited degree = Leishmania b. premonition = resistance to hyperinfection in

endemic areas i. Plasmodia

ii. Hookworm c. pass immunity = maternal Abs

i. Malaria ii. Schistosomiasis

iii. Filariasis 6. eosinophils = kills young Schistosomes and microfilariae

- eosinophilia in ascariasis: seen only in larval stage during migration

- persistent eosinophilia vs. on/off eosinophilia 7. cytokines = TNF and Cachetin

a. protective in experimental malaria in mice b. stimulates killing of Schistosomes by

eosinophils in vitro c. cachexia in trypanosomiasis

The Compromised Host

surgery intubation immunosuppressives chemotherapy aggressive treatment corticosteroids AIDS transfusions prolonged hospitalization

Infections Notably Seen in Immunocompromised States

Amoebiasis Stronglyoidiasis and disseminated strongyloidiasis Trichinosis Toxoplasmosis Cryptosporidiosis Cyclosporiasis Isosporiasis

Prevalance of Parasitic Infections (WHO 1975 – 1995)

Ascariasis, Hookworm 1.3 B each

Amebiasis 1.0% world’s pop

Giardiasis 200 M

Malaria 400-490M; annual deaths 2.2 to 2.5 M

Leishmaniasis 1.2 M

Schistosomiasis 150M; annual deaths 500K to 1 M

Clornorchiasis 13.5 M

Paragonimiasis 2.1 M

Fasciolopsiasis 10 M

Filiariasis(lymphatic) 128 M

Onchocerciasis 17.7 M

Characteristics of Parasitic Diseases

Symptoms are usually proportional to parasitic burden

Reinfections may come from the environment, or autoinfection (Strongyloides and Enterobius)

Chronic infection= Chaga’s disease

Immunocompromising conditions may cause reactivation of latent infection(Toxoplasmosis), increased susceptibility and severe disease

Eosinophilia= larval migration thru vasculature or tissue

JVMM NOTES | PARASITOLOGY| INTRODUCTION & TECHNIQUES IN PARASITOLOGY

UST FMS 2016 | SECOND SEMESTER, 2013-2014 |joelvergilmmendiola@yahoo.com 2

TECHNIQUES IN PARASITOLOGY Examination of Stool

1. Direct Wet Film: NSS and iodine - iodine: not used in direct smear; used only in

the presence of trophozoids 2. Concentration Method: Sedimentation and Flotation

- used when no ova is observed 3. Permanent Stained Slides: E. histolytica 4. Serologic testing plus stool examination: E. histo/dispar,

Giardia, Cryptosporidium 5. Modified AFB: Crytosporidium, Cyclospora, Isospora 6. Special procedures for recovery of helminth larvae and

ova: a. Baermann Apparatus: Strongyloides larva b. Filter Paper Strip Procedure (Harada and

Mori): Strongyloides or Trichostrongylus larvae c. Agar method for evaluation of larval tracts:

whiplike (Strongyloides) ; snakelike (Hk) d. Cellophane Tape Swab for Enterobius and

Taenia ova 7. Schistosomal Hatching Test: miracidia

- operculum opens at pH 7.0 8. Duodenal Sampling and Biopsy

a. Enterotest (String Test): hepatic flukes; Strongyloides, Giardia, Isospora, Cryptosporidium

o patient swallows a gelatin containing a string onto which, upon reaching the duodenum, parasites attach; the string is then pulled out through the mouth

Examination of Blood and other Tissues

- thin smear: detection of P. vivax or P falciparum

- thick smear: determination of parasite load o gametocytes are excluded in the

count 1. Fresh blood: whiplike (microfilariae), undulating and

twisting (trypansosomes) 2. Thin and thick blood smear: Plasmodium 3. Concentration methods: Leishmania, Trypanosomes,

Microfilariadae 4. CSF: Naegleria 5. Tissue imprints after FNAB: Leishmania, Toxoplasma 6. Biopsy and Aspiration 7. Examination of the sputum: Entamoeba, Ascaris

Strongyloides, Paragonimus, Cryptosporidium 8. Urine: Trichomonas, Schistosoma, Wuchereria, Brugia,

Loa, Onchocerca