Parasitology

Monday March 23, 2015

• What is an endoparasite? Can you think of an example of an endoparasite?

• What is an ectoparasite? Can you think of an example of an ectoparasite?

Introduction

• Endoparasites– Nematodes– Cestodes – Trematodes – Protozoa

• Ectoparasites – Ticks, fleas, lice, mites, biting flies

Signs of parasites

• Diarrhea• Vomiting• Anemia• Intestinal obstruction• Malnutrition (hypoproteinemia)• Lack of weight gain• Milk production• (itching)

Transmission

• Direct– Often fecal-oral route

• Transport hosts (intermediate host)– Organism completes a development stage– Short transitory period

• Definitive host (primary host)– Lives, reaches maturity, reproduces

Endoparasite “families”

• Nematodes• Cestodes• Protozoa

Nematodes

• Roundworms– Esophageal worms – Stomach worms– Ascarids– Hookworms– Intestinal threadworms– Whipworms– Pinworms– Heartworms

Roundworm characteristics

• Live and move about in tissues– Intestines, lungs, kidneys, urinary bladder, muscle,

blood

• Eggs and larvae most commonly found in the feces – Intestinal

• Ascarids• Hookworms• Whipworms

Nematodes - Ascarids

• Toxocara species (spp)– Toxocara canis, Toxocara cati

• Eggs– Large, round – oval, dark colored, thick shell

• Stages – Eggs are ingested– Hatch in small intestine– Larvae penetrate mucosa of intestine, migrate through

tissues (liver/heart/lungs) – Larvae are coughed up and swallowed and make way back to

intestine

Adult Worm

Eggs under microscope

• Prenatal/transplacental migration of T. canis– Larvae leave the circulation and are stored in

tissues/organs– Dog becomes pregnant– Larvae leave the tissues at 42-56 day of gestation– Cross placenta and enter lungs of fetuses – Puppies are born with the larvae in their lungs and

cycle continues as the larvae mature and enter intestines

– T. canis and T. cati : some larvae migrate to mammary glands and are ingested by puppies and kittens when they nurse

Zoonosis of Toxocara

• Eggs are ingested by small child

• Larvae hatch and migrate through liver, lungs, eyes

• Called visceral larva migrans

Visceral Larva Migrans

Medication for ascarids/ roundworms

• Fenbendazole, milbemycin oxime, moxidectin, and pyrantel pamoate

• Pyrantel is available in a highly palatable liquid formulation that is readily administered to nursing animals and thus may be considered the preferred treatment for very young pups.

• To prevent environmental contamination, all pups should be routinely treated with pyrantel pamoate at 2, 4, 6, and 8 weeks of age and then placed on a monthly heartworm preventative with efficacy against Toxocara spp.

Roundworms and hookworms (pyrantel)

Symptoms of “Roundworms”• Cough• Shortness of breath• Abdominal pain• Pot bellied appearance• Nausea and • Diarrhea• Blood in the stool• Weight loss• Dull coat• Fatigue• Presence of the worm in vomit or stool

- Hookworms• Ancylostoma species or Uncinaria

stenocephala• Eggs– Oval, thin shelled

• Stages – Eggs are passed into environment– Develop and hatch in environment– Larvae are ingested or penetrate skin– Enter veins (circulatory system) into the lungs– Coughed up and swallowed– Enter small intestine and mature– Transplacental and transmammary migration also

Nematodes - Hookworms

Zoonosis of Hookworms

• Cutaneous larva migrans

Nematodes - Whipworms

• Tricherus Vulpis• Eggs– Thick brown yellow shell with a clear polar plug at each

end• Stages– Eggs are ingested– Larvae hatch into small intestines– Penetrate mucosa, migrate and return to intestines– Migrate to cecumand colon and bury their anterior ends

into the mucosa and mature to adult stage

Whipworm Egg

Whipworms

Medications for Whipworms

• febantel , pyrantel pamoate and praziquantel – Drontal

• fenbendazole – Panacur®

• To achieve control, treatment can be administered once a month for 3 months.

• Milbemycin oxime (found in: interceptor, triflexis, sentinel)

Tuesday March 24, 2015A._____________

B. ____________

C. ____________

Name these three parasites…

Nematodes - Heartworms

• Dirofilaria immitis • Parasite of the circulatory system• In dogs: right ventricle of heart and pulmonary

arteries• Dog is definitive host

Heartworm

• Adult is called dirofilaria immitis• Larvae are called microfilaria– Found in the bloodstream– Migrate to the heart and lungs

• Intermediate host is mosquito

Heartworm

• Heartworm disease in dogs• HARD in cats– Heartworm associated respiratory disease

Medication:Preventative - IvermectinTreatment – melarsomine

(Immiticide)

Cestodes

• Tapeworm spp– Dipyldium caninum– Taenia taeniaeformis

• Flea is intermediary host– Rodents, rabbits, deer = different species of

tapeworms• Primary host (canine or feline) ingest the

intermediary host• Eggs– Thin shelled, when found under microscope may

find “packets”– Proglottids (tapeworm body segments) are filled

with thousands of egg packets

Taenia or dipylidium

Tapeworms

Medication for tapeworms

• Praziquantel (Droncit)• Epsiprantel, and • Fenbendazole

• Preventative flea control!

Protozoa

• Single celled organism – (have a nucleus so are eukaryotic)

• Giardhia– dogs, cats, humans, beavers

• Coccidia – Isospora– Cryptosporidium– Toxoplasma gondii (cat is definitive host)

Giardia

• Live in the intestines– Villi become damaged/ malabsoption occurs

• From contaminated items or environment

• Treated with metronidazole

• Prevention– Cleanliness– Water, ground surface, soil, undercooked foods– Often fecal- oral transmission

Giardia - two formsTrophozites

• Feeding stage• Found in the small intestine

Oocysts

• Thick walled spore that protects

• Cyst is ingested, wall is digested away, trophozite is released and immediate divides into two organisms

• Binary fusion

Coccidia

• Isospora– Oocysts in the feces– Sporulates (divide/ become infective)– 2 sporocysts• Each enclose four sporozoites• Total of 8 infective forms per oocyst

– Walls are digested and sporozoites penetrate intestinal cells

– Grow, replicate, mature, “reproduce”– After fertilization, oocyst is produced and cycle

starts over– Causes diarrhea• Affects very young and immune compromised animals• If severe infestation can mimic parvovirus and even be

fatal

• Toxoplasma and Cryptosporidium– Intestinal– Same type of life cycle as Isospora– Toxoplasma causes birth defects in humans– Cryptosporidium causes severe diarrhea

Isospora

isospora

Toxoplasma Gondii

cryptosporidium

Name the three parasites…

Roundworm and hookworm eggs

Answerwhipworm

Ascarid(roundworm)

Ectoparasites

• Fleas• Ticks • Mites

Flea

• Ctenocephalides felis– Cat flea

• Not host specific• 65 - 80 °• Warm, humid

Fleas…a vicious (life) cycle

• Flea lifecycle stages:

• Egg - The flea egg hatches in 2-21 days, depending on environmental conditions.

• Three larval stages - The larval stages grow and undergo their moults over about 9-15 days.

• The pupal stage (cocoon) - The cocoon is the crux of flea infestation persistence in the house-hold. It generally hatches in 1-2 weeks, but can last up to a year.

• The adult flea - Adult fleas can live for some weeks (maximum of about 2 months if no host is present) in ideal conditions.

Flea disease

• Anemia

• Tapeworms

• Plague – (Yersinia pestis)

• Catscratch fever – (Bartonella henselae infection)

Ticks – multiple host cycle

Tick life stages

Common species of ticks

• Two families of ticks –soft ticks and hard ticks• Ixodid family (hard ticks)– Brown dog tick– Lone star tick– Deer tick

• Diseases– babesia, ehrlichia, rocky mountain spotted tick

fever, lyme, tularemia, anaplasmosis

Brown dog tick

• Tick and Fleas medications are aimed at killing different stages of the parasites– Eggs– Larvae– Pupae (cocoons – fleas)– Nymphs– Adults

• Neurotoxins – Fipronil (Frontline) – Imidaclopride (Advantix)– Permethrin (common brands)

Only kill adultsOther ingredients work synergistically as IGRs (Insect

Growth Regulators)RepellantsAmitraz (for ticks)Cats- Use caution!!!

Mites

• Sarcoptic mites– Sarcoptes scabiei– Burrow into the epidermis• Pruritic skin condition• Rash• Scaling, crusting, excoriation

– 4 stage life cycle spent on the host• Eggs• Larvae• Nymph• Adult (takes 12- 17 days to become adult)

– Contagious by direct contact• Zoonotic but self limiting in people

Sarcoptic mange

Ear Mites

• Otodectes cynotis– Reside within external ear canal– 5 stage lifecycle lived on host• Egg, larva, protonymph, deutonymph, adult

– Common cause of otitis externa in dogs, cats, ferrets

– Feed on dead cells on the ear canal / produce intense irritation

– Head shaking/ scratching ears• Aural hematomas

– Sometimes can be seen with otoscope• Prepared slide• Brown exudate usually will have mites moving around

Ear mites

Demodex

• Demodex Mites• Live in hair follicles and sebaceous glands– Normal and nonpathogenic

• Host specific / not transmissible

• An increase of these mites is called demodicosis– Immune system related– May be localized to one area or generalized / all

over

Demodex under the microscope

• Cheyletiella– Live on surface of skin – ingesting skin “debris”– Host is dog, cat, rabbit– “Walking dandruff”– Diagnostics• View moving “flakes” through magnifying glass• Cellophane tape• Flea comb• Area: dorsal midline and head

Cheyletiella

Ringworm•Not a “worm”•Is a fungus•Zoonotic

•Keratin seeking•Dermatophyte •Lesions are circular