Biology of Parasitism Part 2 PDF

PARASITOLOGY 2 Biology of Parasitism II Dr. Cassan Pulaski SLIDE DECK CREDIT: NC STATE Veterinary Parasitology Group (VMP 930)  Hemoflagellates (in blood) Mucoflagellate...

PARASITOLOGY 2 Biology of Parasitism II Dr. Cassan Pulaski SLIDE DECK CREDIT: NC STATE Veterinary Parasitology Group (VMP 930)  Hemoflagellates (in blood) Mucoflagellates Parasite Groups Protozoa Coccidians Piroplasms (in Blood Cells) Infectious diseases Trematodes flukes (flat) Sun mediate  Microbiology Cestodes hemaphroditic  Virology Helminths  Bacteriology Nematodes  Mycology Acanthocephalans "thorny-headed worms" fish mainly birds - Ticks  Parasitology Mites  Protozoology Arthropods  Helminthology Lice  Entomology Fleas Flies  Types of Life Cycles – Direct life cycle: parasite does not require an intermediate host. The infective stage (egg, cyst, or larva) is in the environment. – Indirect life cycle: parasite requires an intermediate host. – Facultative Indirect life cycle: parasite may use a paratenic host Paratenic host is not necessary (Facultative = “Optional”) ↳ intermediate host (doesn't developmove life stages win that specific host) Parasite Stages – Various terms for stages depending on the parasite group (worms, protozoa, arthropods) – Ex. Worms Larval stage - sexually immature form of the parasite (mostly L3 is infective stage) Adult stage - sexually mature form of the parasite Hosts – Definitive host (primary host): animal infected by the sexually mature parasite – Intermediate host: animal infected by larval stage(s) that continue development, but do not mature Vector: transmits a pathogen from one host to another – Mechanical vector: not necessary for pathogen development (face fly proboscis) – Biological vector: necessary for pathogen development (tick) – Paratenic host (transport host): host infected by a larval stage that does not develop further. Lex Cow as. paratenic host for – Aberrant host (dead-end host): host that is accidently infected and does not transmit parasite further. toxoplasma Other Concepts Host Specificity – Degree of Host-Parasite compatibility – High Host specificity Parasite can infect only one or a few host species (Oxyuris, Lice, Eimeria, sexual stages of Toxoplasma) ; EPM-horses ↳ coxidia ↳ pin worms – Low Host Specificity specificity for ruminants of ruminants high host Parasite can infect several or many host species (Physaloptera, Fleas, asexual stages of Toxoplasma) Prepatent v/s Patent – Prepatent Period (PPP): developmental / maturation time needed between time of infection to the production of offspring. Determines the timing of treatment for control measures. – Patent: an infection in which sexually mature parasites are generating offspring. ↳ can detect parasite/infection (passing offspring) Zoonosis: an animal disease transmitted to humans  (pinworms Helminth Life Cycles Life Cycle Type # Direct Life Cycle fecal-oval (pinworms) Hosts Definitive Host (horse-pinworms) Oxyuris equi is the equine Parasite Stages pinworm that causes pruritus of Adult the perianal region, resulting in Ovum or Ova alopecia and a bald tail-head. Host Specificity High Zoonotic No Direct Life Cycles have a single host (Definitive Host) and do not require an Intermediate Host to complete the parasite's life cycle. Many Direct Life Cycles involve fecal-oral transmission. The Definitive Host is the host in which the Adult or sexually mature parasite resides. For some parasitic worms, Ova (eggs) are produced by Adult worms and the Ova are passed in the feces. An Ovum provides a protective shell in which an Infective Larvae develops. The Ova are often the diagnostic stages for many parasites.  "Stomach worms" Helminth Life Cycles Life Cycle Type Indirect Life Cycle Hosts Definitive Host Intermediate Host Paratenic Host Sylvatic Host Physaloptera rara is a Reservoir Host stomach worm of pets and wildlife. It may cause Parasite Stages gastritis with gastric Adult ulcers. Ovum or Ova Infective larvae Arrested larvae (Hypobiotic larvae) * must have beetle as int. to infect Host Specificity An Indirect Life Cycle requires an Intermediate Host in which development of the parasite is necessary. definitive host Low. Non-domestic Definitive Hosts are called Reservoir Hosts or Sylvatic Hosts. Infective Larvae may develop within the Intermediate Host to later infect the Definitive Host. A Paratenic Host is not required for the development of the parasite but may transport Arrested Larvae to the Definitive Host. Zoonotic No parasiticidea multi/3dausfenbendazole  Helminth Life Cycles (brown Stomach worm) common in cool climates Life Cycle Type Ostertagia ostertagi is called the brown stomach worm of cattle. Direct Life Cycle Larvae and adult worms cause Pasture-borne Parasite dysfunction of the abomasal mucosa, resulting in diarrhea, Hosts anorexia, and protein catabolism. Definitive Host Parasite Stages Cybernation-like Adult stage until environmental Ovum or Ova conditions are right) can see clinical when all come out signs of Free-living larvae time) arrested Stage at same Infective larvae Arrested larvae (Hypobiotic larvae) Host Specificity High Many pasture-borne parasites, such as Ostertagia spp., have Direct Life Cycles. When Ova are passed in the feces, Free-living Larvae hatch and develop on pasture. Zoonotic The Free-living Larvae (L1 & L2) eventually develop into Infective Larvae (L3), which are accidentally ingested by the Definitive Host while grazing. No After ingestion, the Infective Larvae develop in the abomasal mucosa and become Arrested Larvae, also known as Hypobiotic Larvae. Arrested Larvae will re-activate & re-emerge into the lumen of the abomasum and become Adult worms.  Protozoan Life Cycles Hemoflagellates Life Cycle Type Indirect Life Cycle Trypanosoma cruzi is a vector- borne pathogen transmitted by Continuous Life Cycle triatomine bugs ("kissing bugs") that can cause Chagas disease. Its Hosts tropism for cardiac muscle often Definitive Host causes damage to the heart. Intermediate Host can also cause colon Vector mega Life Cycle Processes Binary Fission Clonal Replication Parasite Stages Asexual Stages only Amastigote Hemoflagellates, such as Trypanosoma cruzi, have Indirect Life Cycles, which includes a mammalian Definitive Trypomastigote Host and an insect Intermediate Host. The insect Intermediate Host is also called the Vector for the protozoan. Epimastigote The protozoa multiply asexually by Binary Fission or Clonal Replication, resulting in Asexual Stages Only. Without control by host immunity, some parasites, like Trypanosoma cruzi, will continue to multiply until they * Host Specificity overwhelm the host. This is called a Continuous Life Cycle. Low Life Cycle forms, for Trypanosoma cruzi, include Amastigotes in the mammalian tissues, Trypomastigotes in the Zoonotic mammalian blood, and Epimastigotes in the insect gut. * Yes  (duodenalis) Protozoan Life Cycles Mucoflagellates Life Cycle Type Direct Life Cycle Hosts Definitive Host Giardia spp. are protozoa parasites that infect the Parasite Stages gastrointestinal tracts of animals Asexual Stages only and can cause diarrhea. Giardia Trophozoite cysts are transmitted via fecal- oral route. Cyst Life Cycle Processes Binary Fission Clonal Replication Host Specificity High  Mucoflagellates, such as Giardia canis, have Direct Life Cycles, which only requires the Definitive Host.  The protozoa multiply asexually by Binary Fission or Clonal Replication, resulting in Asexual Stages Only. Zoonotic  Life Cycle forms include an active Trophozoite with in the Definitive Host and a Cyst that contaminates the environment.  The Definitive Host is infected by ingesting the Cyst stage. No?  Like viruses and bacteria, replication is necessary for pathology caused by protozoa. * amount contributes to pathology low #S-healthy animal ; high #S- diarrhea Pathology: Host organ dysfunction Replication Giardia sp. (binary fission)  Cystoisospora spp. are Protozoan Life Cycles protozoa parasites that infect Coccidia the gastrointestinal tract of carnivores, causing diarrhea Life Cycle Type primarily in young or Direct Life Cycle immunocompromised Facultative Indirect Life Cycle animals. It is transmitted via Asexual Cycle fecal-oral route and can be Sexual Cycle prevented with proper sanitation. Hosts Definitive Host Paratenic Host Parasite Stages Unsporulated Oocyst Sporulates Oocyst Host Specificity Sporozoites High Meront Merozoites Zoonotic Gametocytes No Zygote  Most coccidians have Direct Life Cycles, which only requires the Definitive Host and fecal-oral transmission. Life Cycle Processes  However, some coccidia, like Cystoisospora spp., have Facultative Indirect Life Cycles, which provides the use of unnecessary Paratenic Binary Fission Hosts to maintain the life cycle. Paratenic Hosts harbor Cystozoites which infect the Definitive Host upon ingestion. Sporulation  Coccidians utilize Sexual & Asexual Cycles within the Definitive Host.  Unsporulated Oocysts are passed in the host’s feces. These go through Sporulation, resulting in an infective Sporulated Oocysts Merogony  After being ingested, the Sporulated Oocyst releases Sporozoites which invade gut cells. This begins the Asexual Cycle: Sporozoites Gametogony multiply by Binary Fission or Merogony producing a Meront full of Merozoites. Fertilization  The Sexual Cycle occurs when Merozoites differentiate into Gametocytes via Gametogony. After Fertilization, the resulting Zygote develops into an Unsporulated Oocyst to be passed out in the feces.  (Brown tick) Arthropod Life Cycles Life Cycle Type Simple Metamorphosis 1-HostTick 2-HostTick Dermacentor variabilis is called the American Dog Tick. Besides 3-Host Tick causing irritation, blood loss and Tick Paralysis, this tick is Parasite Stages also a vector for Rickettsia Eggs rickettsia (Rocky Mountain Larvae Spotted Fever). Nymphs Adults Male Female Host Specificity Like other arachnids, ticks have eight legs, except for the six-legged larvae. Low Ticks develop from Larvae to Adults through a process of Simple Metamorphosis. Simple Metamorphosis is when all life stages of an arthropod look similar, except for size and minor differences. Engorged Female ticks drop off the host and deposit Eggs in the environment. Zoonotic Six-legged Larvae hatch from these Eggs and feed on a host. The larvae develop and molt to become eight-legged 1st Nymphs, which also feed. Yes After feeding, the 1st Nymph develops and molts into the 2nd Nymph. Like wise, the 2nd Nymphs feed, develop, and molt into Adult ticks. Male and Female Adult ticks feed and mate on the host. The engorged Female then drops off the host to lay Eggs in the environment. Dermacentor variabilis is a 3-Host Tick because it feeds on 3 different hosts. Other species of ticks are 1-Host or 2-Host Ticks.  Arthropod Life Cycles Life Cycle Type Simple Metamorphosis Hemimetabolous Parasite Stages Nits Trichodectes canis is a chewing Nymphs louse of dogs. Chewing Lice feed on skin, fur, feathers, and debris; Adults and cause general irritation, Male pruritus, and alopecia. Other lice Female are Sucking Lice, which feed on blood. Host Specificity High Zoonotic Lice develop from Nymphs to Adults through a process of Simple Metamorphosis or Hemimetabolous development. No Simple Metamorphosis occurs when all life stages have a similar appearance, except for size. Male & Female Lice mate on the host and the Female louse cements Eggs (aka Nits) on the hair or feather shaft of the host. Nymphs hatch from the Nits, then feed and molt to the next stage. There are usually several molts before reaching the Adult stage. All stages, from Nits to Nymphs to Adults, remain on the host.  Arthropod Life Cycles Life Cycle Type Complex Metamorphosis Holometabolous Parasite Stages Ctenocephalides felis is called Eggs the Cat Flea but is found on Larvae dogs as well as many other Pupae hosts. Fleas cause irritation, pruritus, alopecia, blood loss, Puparium and Flea Allergy Dermatitis Adults (FAD). Male Female Host Specificity Low Fleas develop from Eggs to Adults through a process of Complex Metamorphosis or Holometabolous development. Complex Metamorphosis occurs when the life stages have a dissimilar appearance. Zoonotic Male and Female fleas feed and mate on the host. Eggs are deposited on the host; but fall off into the environment. Yes In the environment, Larvae hatch from the Eggs and develop through 3 Larval Stages via 2 molts. The caterpillar-like Larvae feed on environmental debris. The 3rd Larval Stage builds a cocoon (aka Puparium) in which the Pupa develops into Adult fleas. When a host passes by, the Adult flea will emerge from the Puparium and attack the host. The Parasitic Lifestyle is Highly Successful Every host has a long list of parasites that can infect it Evolved independently in nearly every phylum of animals and plants Usually do not directly cause mortality – co-evolved with host – infections are chronic and may be disabling – but only in a small % of hosts – ultimate goal is to reproduce  Infection ≠ Infectious ≠ Disease Infection = presence of an agent that has the potential to cause disease Infectious = infected host capable of transmitting infection to another host – (“Contagious” in virology) – versus Infective = parasite stage capable of invading the next host Disease = the occurrence of dysfunction / pathology Infection ≠ Infectious ≠ Disease  Parasites and Hosts Co-evolved It is normal and natural for animals (and humans) to be infected with parasites Infection ≠ Disease  Parasite Pathogenesis  Pathogenesis (how the pathogen causes disease)  Production or Development of Disease  Forms of Pathogenesis  Trauma  Direct destruction of the host cells or tissues  Eimeria, Babesia, Sarcoptes, Haemonchus, Small Strongyles  Indirect destruction of host cells or tissues  Tritrichomonas, Giardia, Ascaris  Organ occlusion  Parascaris, Dirofilaria, Heterobilharzia, Babesia  Nutrient Robbing  Tapeworms, Ascaris Traumatic destruction of epithelial cells  Excretion of Toxins or Other Pathogens  Tritrichomonas, Fasciola, Nanophyetus  Interactions with host immune / inflammatory responses  Demodex, Dirofilaria, Leishmania, Fleas  Canti inflammatory) (inflammatory R.M. Maizels, Parasitology (2009) “Exploring the immunology of parasitism--from surface antigens to the hygiene hypothesis” Parasite Impact on Host Parasite effects on hosts are a continuum Parasite number and pathogenicity determine disease state – No effect on host – Subclinical No obvious signs; subtle performance losses – Clinical Disease manifestation Clinical judgement: “Is the parasite’s effect on the patient important enough to justify treatment?” Image from internet, believed to originate from Dr. Joel Weinstock at Coronado Biosciences