Week 9 - Introduction to infectious diseases in animals Flashcards
What are the INFECTIOUS DISEASES -
MICROBIAL PATHOGENS
- Bacteria
- Fungi
- Algae
- Protists
- Viruses
What is the difference between Eukaryotes vs Prokaryotes
- Size
- Metabolism
- Cell organisation
- Replication
- Maintenance of shape
- Nucleic acid handling
- Ribosomal structure
- Genome
What are the Metabolic Diversity
• Bacteria can catabolise all naturally occurring organic compounds • Photoautotrophs • Chemoautotrophs • Photoheterotrophs • Chemoheterotrophs - all the pathogenic bacteria
Diffference between Viruses vs Bacteria
- Structural Unit
- Genome
- Replication
- Generation of Energy
- Size
Habitats of Pathogens
• Pathogenic bacteria and fungi originally
free-living
• Obligate parasites not able to survive
independently
• Saprophytes can live freely, don’t need
host
• All viruses obligate parasites, but not
necessarily in diseased animal
Microorganisms in the Environment
- Ubiquity of microorganisms complicates diagnosis
- Microorganisms in the environment can be mistaken for pathogens
- In some cases they are
- How can we determine their significance?
Differencee between Infection vs Disease
- Relatively few bacteria, fungi and viruses pathogenic
- Even most pathogens more frequently cause subclinical infections
- Infections (entry into the body) occur frequently
- Disease (loss of function) does not
What is the characteristics of bacteria etc in normal flora
- Always present
- Variation
- Role in health
- Protective role
- Source of opportunists
- Significance in diagnosis
Specific Sites for intrusion
- Mouth and Nasopharynx
- Stomach
- Duodenum, Jejunum and Ileum
- Large Intestine
- Trachea, Bronchi and Lungs
- Vulva and Prepuce
- Vagina
- Skin
- Mammary Gland
What is Koch’s Postulates
- Found in lesions
- Isolated in pure culture
- Experimental reproduction
- Recovered from experimental disease
How do you make a Microbiological Diagnosis
• If I detect an organism: – Is it from the animal? – Is it the one causing disease? – Is it the only one causing disease? • If I don’t detect an organism: – Is it because there wasn’t one there? – Is it because it didn’t survive the trip? – Did I look for the right one?
How to make the Correct Diagnosis
- Collect the sample from the right animal and the right place
- Treat the sample carefully and examine it as quickly as possible
- Interpret the results in the light of the situation you are presented with - common things occur commonly
What is the definition of a PARASITES
“Eukaryotic organisms that live in or on a host organism and cause harm to the host without immediately killing it.”
What are the major group causing disease
Features*
Endo- and ecto-parasites
Life cycles: direct; indirect
Infections: clinical/disease; subclinical
Names; host and organ system affected
Endemic; non-endemic (“exotic”)
Some are zoonotic*
What are PROTOZOA
What are they? : Unicellular organisms (“eukaryotic microbes”)
Biology : Free-living (millions); Parasitic (many!)
Significance : Socio-economic importance
Pathogenesis : Intraintestinal Extraintestinal
Reproduction : Intracellular Asexual, Extracellular Sexual
Life cycles : Direct Indirect
Size : 5-40 µm
Features : Vary, but characteristic for each ‘group’
Locomotion : Gliding, via flagella, cilia or pseudopodia, other
SELECTED GROUPS OF PROTOZOA
Apicomplexa
Flagellates
Ciliates
Amoebae
What is Giardia (cf. Cryptosporidium) (direct life cycle)
Faecal-oral transmission Often young animals and humans Often clinical signs (days) Acute and chronic infections Replication in small intestine
What does Giardia do
Colonization/replicate in the small intestine Epithelial cell loss Decreased surface area and enzymes Malabsorption Inflammation Increased motility
What is TREMATODES
- Flukes or digeneans
- Usually flat, unsegmented worms*
- Mostly hermaphrodites
- All have indirect life cycles*
- Snails as intermediate hosts (others)
- Larval, juvenile and adult stages
- Acute and chronic infections
- Clinical and subclinical
What is CESTODES
Tapeworms
Flat, segmented worms; no gut; scolex*
Hermaphrodites
All have indirect life cycles
Adult worm in intestine; larva in tissues (damage)*
Usually chronic infections (rarely acute)
Difficult to diagnose in live animal
What are NEMATODES
Roundworms
Round in cross-section
Exist as two sexes (dioecious)
Features*
Direct or indirect life cycles
Acute and chronic infections
Clinical and subclinical
What is an example of trematodes
Fasciola hepatica (liver fluke)
What is the life cycle of Fasciola hepatica (liver fluke)
First host (like snails) will be found and transported to the grass which is then consumed be animals or humans
What is Echinococcus granulosus
(hydatid tapeworm)
