Internal Parasites
- Gains protections an d nutrition from the host at the expense of the host
- Live inside the body of an animal
- Differ in size
- Differ in location w/in the body
- Differ in the species of animal they affect
Definitive host
animal harboring sexually mature parasite
Intermediate host
animal used by the immature stages of the parasite to continue developmen
Paratenic host
animal serving as a transport host for immature stages of the parasite, no development occurs
Prepatent period
time elapsed between infection with parasite and when it reaches reproductive maturity
Ways internal parasites cause damage to the host animal
o Malnutrition- compete w/ host for ingested food
o Mechanical- destroy tissue, cause obstructions
o Blood loss- anemia
Ways in which animals acquire internal parasites
- Environment- directly eating larvae (poop)
- Eating intermediate host (flee)
- Parasite actively penetrates through the principle host and migrates
- Intermediate host is a vector and transmits parasite (mosquito)
- Eating the paratenic host (possum)
- Maternal transmission- transplacental or through milk
Appearance of parasitized animal
• Mild- inapparent
• Severe- underweight, dull hair coat, lethargy
• Other clinical signs:
diarrhea, vomiting, blood in the stool
Diagnosis of parasitism
- Detection of immature parasites (i.e. larva) or parasite eggs in the animal’s feces, blood, or urine
- Presence of adult parasites in feces or vomit
Administration of anthelmintics
o affect the parasites CNS leading to death or paralysis
o some cause digestion of the parasite
Effect of host and environment on parasitism
- Older animals more resistant to parasitic infection- in younger animals
- Parasites reproduce better in warm, moist conditions
Control and prevention of parasitism
- Daily removal of feces from housing areas
- Prevent ingestion of intermediate or paratenic hosts
- Perform routine laboratory tests to screen for parasite infections
Internal Parasites- list
- Nematodes (Roundworms)
- Cestodes (Tapeworms)
- Trematodes (Fluke worms)
- Protozoa
Nematodes
- Most important group
- Found in many different organs w/in the body
- Adults can be seen w/ the unaided eyeà elongated, cylindrical
- There are male and female adult worms
Encyst
when nematode larva goes dormant. When realize not the definitive host.
Cestodes
- Adult parasites live in the intestine
- All have intermediate hosts
- Long flat worms divided into segments-> scolex, proglottids
Trematodes
- Usually found in the intestine, liver, lung
- Use the snail as an intermediate host
- Flat worms with leaf-shaped body
Protozoa
- Unicellular organisms
- Found in different organs w/in the body
- Only visible with a microscope
Ancylostoma caninum
- “Hookworm”
- • Eggs are oval w/ thin shells and multiple cell clusters
- Importance->Anemia, diarrhea, malabsorption, cutaneous larva migrans
- Diagnosis->Eggs in fecal flotation
- Control-> Treat infected dogs, remove feces
Cutaneous Larva Migrans
creaping eruptions
• Skin inflammation caused by a migrating roundworm larva
• Syndrome Human-> itchy, reddish, raised skin lesion that follows a serpentine pattern
Animal-> anemia, diarrhea, malabsorption in puppies
• Incubation period is 2-3 days
• Mortality: none
• Occurrence- Areas w/ warm moist climate and sandy soil
• Transmission- Skin contact w/ infective larva in soil contaminated w/ dog and cat feces
• Diagnosis - Syndrome, history of exposure
• Treatment- Antiparasitics, antipruritics, antibiotics
Cutaneous Larva Migrans Causative parasites can include:
Causative parasites can include:
o Ancylostoma spp., Uncinaria spp.
o Strongyloides stercolaris
Control and prevention Cutaneous Larva Migrans
o Regular deworming of dogs and cats
o Prohibition of dogs and cats on playgrounds and beaches
o Wear protective clothing when in contact with potentially contaminated soil
Diagnosis of heartworm
Microfilaria in blood
blood smear, microhematocrit tube, Knott’s test, filter test
antigen test, antibody test
Control of heartworm
Preventative drug treatment
treat infected dogs
