Veterinary Parasitology I

Veterinary Parasitology I

• Course date: 05/11/2022
• Course instructor: Dr. Walid Darwiche
• Course location: Lebanese University
• Course: Veterinary Parasitology I
• Parasitology 1 (course name)

Definitions

• Parasites, parasitism, and parasitic diseases are defined.

What is Veterinary Parasitology?

• Veterinary parasitology is the study of parasitic organisms and their diseases in animals.
• Animal diseases can have non-infectious or infectious origins.
  • Non-infectious diseases: genetic defects, physiological abnormalities, structural dysfunction, external factors (injury, radiation, or poisoning).
  • Infectious diseases: associated with invasive, self-replicating agents that have evolved to occupy an animal's body.

Studies in Infectious Diseases

• Microbiology: Viruses, bacteria, fungi.
• Parasitology: protozoa, trematodes (flukes), cestodes (tapeworms), nematodes (roundworms), and minor groups.
• Medical/Veterinary protozoology: single-celled eukaryotic organisms.
• Helminthology: trematodes, cestodes, nematodes.
• Medical/Veterinary entomology: parasitic arthropods (insects, ticks, mites).

Parasites in Practice

• Effort and time veterinary practices spend on parasite issues.
• Parasites often diagnosed.
• Parasites veterinary practices often attempt to manage.

Host-Parasite Relationships

• Parasitism is part of a spectrum of intimate zoological relationships.
  • Mutualism: both partners benefit (obligatory in many cases).
    • Example: alligator and a bird.
  • Commensalism: one partner benefits, the other is neither harmed nor helped. Example: remora and a zebra shark.
  • Parasitism: one participant harms the other. Example: a tick on a dog.

Classification

• Animal kingdom is divided into 35 phyla.
• Classified further into class, order, family, genus, and species. Subclass, suborder, and superfamily can also be important.

Nomenclature

• Defining every organism using a combination of its genus and species name.
• Example: Babesia divergens, Babesia bovis, Babesia bigemina.
• Using the suffix "-osis" is common in parasitology for naming the disease caused by a parasite.

Differences in Parasite Localization

• Parasites can be broadly categorized by their location.
  • Ectoparasites: live on the surface or within a host's superficial tissues, or adjacent underlying tissues.
  • Endoparasites: live inside a host and can be found in any tissue of the body, except, bones and keratin.

Relationship of the Parasite to the Tissue

• Extracellular parasites: live on or within the host's tissues but don't penetrate host cells.
• Intracellular parasites: live inside a host cell; affecting gene expression.

Concept of Micro and Macro Parasites

• Microparasites: multiply within the host, increasing the potential for a large infection. Usually include bacteria and protozoa.
• Macroparasites: do not increase in number in the host. They produce eggs/larvae that are disseminated into the environment. Host only accommodates their development.

Parasite Modes of Transmission

• Hosts are infected through ingestion or skin penetration.
• Some are transmitted by contact or predation.
• Others are spread through nostrils, external genitalia, or transplacental/transmammary routes.

Different Modes of Parasitism

• Obligate Parasite-completely dependent during its entire life cycle, such as lice, ear mites.
• Facultative Parasite - the organism has both parasitic and nonparasitic modes of life and doesn't strictly depend.
• Accidental Parasite- attacks an unnatural host successfully, such as heartworms in humans.
• Erratic Parasite- wanders into an organ not usually found, such as a heartworm in an eye.

Host

• Final (Definitive) Host: The host where the parasite reaches maturity and reproduces sexually.
• Intermediate Host: The host where the parasite develops asexually.
• Reservoir Host: A host that harbors the parasite without showing symptoms of disease and can be a source of infection.
• Vector: An organism that transmits the parasite from one host to another, often by an insect.

Parasitic Diseases

• Parasitic disease or parasitosis is an impairment of health.
• Understanding the etiology, pathogenesis (the mechanisms causing the disease), and symptoms is important.

Epidemiological Terms

• Epidemiology: study of disease in populations
• Endemic: disease occurring regularly in a certain area.
• Sporadic: a disease occurring infrequently in a certain area.
• Epidemic: high occurrence of a disease in a certain area or place.
• Pandemic: a global outbreak of disease.

Terminology Used In Parasitic Diseases

• Incubation Period: the time between parasite entry and symptoms appearing.
• Prepatent period: time between infection and first detection of eggs/larvae in the host.

Methods of Dispersal of Parasites

• Parasites can be dispersed mechanically by water and other means such as fomites.
• Humans may also help spread some parasites, such as by creating irrigation canals to support their intermediate hosts.

Parasite-Induced Host Behavioral Changes

• Parasites can induce behavioral changes in their host, such as making some hosts more susceptible to predation.