Pathogens

• What are pathogens

  Pathogens are microorganisms that cause diseases
• Structure of bacteria

  Single-celled organisms

  Prokaryotes

  They have a cell wall but no membrane- bound nucleus or contain mitochondria
• Structure of Virus

  Simple organisms

  Consists of genetic material- DNA or RNA

  Surrounded by protective protein ‘coat’

  Non-living organisms as they require a host cell in order to reproduce
• Structure of Protozoa

  Single Celled Organism

  Display Animal like characteristics such as movement and feeding.
• Structure of Parasite

  Any organism that lives on another organism, pathogenic parasites in animals tend to either be protozoa, ticks or worms.
• Sizes of pathogens

  Bacteria- measured in micrometers

  Virus- Measured in nanometers

  Fungi- Varies enormously from microscopic to very large

  Protozoa- microscopic

  Parasite- Vary in size
• Replication of Bacteria

  Replicate asexually using the process binary fission.

  When a cell is big enough it replicated its genetic material and divides in two, each cell contains same genetic material.

  Genetic material can be transferred between different bacterial cells through process of conjugation ( facilitates bacterial resistance to antibiotic)
• Replication of Virus

  So small they can get into cells, then reproduce themselves by taking over cells normal reproduction process.
• Replication of Fungi

  Can reproduce sexually and asexually.

  Sexual reproduction occurs when two parent cells of opposite strains fuse, leads to new class that’s are genetically different to parent.

  In asexual reproduction the fungus develops spores which are genetically identical to the parent cells, spores then disperse and grow into new hyphae, yeasts reproduce asexually by budding.
• Replication of protozoa

  Reproduce sexually or asexually .

  Most common asexual is binary fission as per bacteria.

  However other asexual includes budding and plasmotomy
• Replication of Parasites

  Fleas, ticks, mites, lice and worms reproduce by laying eggs inside the host
• What is a Parasite?

  Organism that obtains food from the host organism.
• Ectoparasite

  Parasite that lives on the skin of the animal
• Two main types of worms

  Roundworms- Round, white and grow up to 15cm

  Tapeworms- Flat, consisting of a head with a body made of independent segments, grow up to 60cm
• Symptoms of worms:

  • Presence of worms in faeces or vomit
  • Diarrhoea
  • Anaemia
  • Dehydration
  • Loss of weight
  • Pot belly
  • Behaviour indicating an itching anus

  However they may only appear when the infestation is advanced.
• Lifecycle of roundworm

  Eggs are laid in testing and pass out body in dropping or vomit

  Larvae develop after 2 weeks whilst in eggshells. Eggs are sticky and attach to animals fur and ingested when animal cleans itself.

  Once inside animals stomach, egg hatches and 2nd stage larvae moves to small intestine and then liver.

  3rd stage larvae develops in liver then move to blood vessels into heart and lungs, animals will cough up larvae and swallow it.

  Larvae makes its way through stomach to small intestine where it reaches adulthood and begins to lay more eggs.
• How long is the lifecycle of a roundworm?

  About six weeks
• How can roundworms affect offsprin?

  If an animal is pregnant the roundworm can infect the unborn animal, it’s not uncommon for young puppies to already have roundworms and hence puppies and kittens need worming.
• Common roundworms in the UK

  Toxocara canis - affects dogs

  Toxocara cati- affects cats

  Toxocaris leonina- affects both
• Lifecycle of tapeworm

  • Segments of tapeworm containing eggs, separate form main body
  • Eggs are ingested by other organisms, ‘flea tapeworms’ the larvae can develop into cysts and can be carried into organism if swallowed.
  • Ingested tapeworm develops into adulthood in small intestine
• Common tapeworms

  • Dipylidium caninum
  • Taenia
  • Echinococcus granulosa -zoonotic
• Other worms that can affect animals in the Uk

  Hookworms - resemble roundworms but have to teeth to grip small intestine

  Whipworms- thick end and thin end, resembling whip and live in large intestine

  Lungworms- carried by snails and slugs, infect dogs and cats, live in animals heart and blood vessels that supply lungs

  Symptoms are breathlessness and coughing.

  Liver Flukes- flatworm and parasite of liver, affect all mammals prevalent in sheep and cause death
• Treatment of worms

  De-worming medication

  Tablets, injections, spots on collar especially in puppies and kittens
• Prevention of worms

  Keep animals free from fleas, dispose of faeces promptly, restrict movement outdoors especially areas with droppings.
• What are fleas

  Ectoparasites that live on the skin and feed off animals blood.
• Symptoms of fleas

  • Skin irritation
  • Other allergic reactions
  • Blood infections
• Evidence for fleas

  Flea ‘dirt’ - digested blood excreted by adult fleas, can be seen when combing animal.

  Fleas can also carry pathogenic diseases which cause more serious problems.

  Example - Deadly rabbit disease myxmatosis
• Life stage of flea

  Egg stage: Hatches in 2-14 days

  Larvae stage: lasts 4-20 days, larvae are blind and feed on pre- digested blood passed from adults. At end of stage, larvae spins cocoon.

  Cocoon or pupae stage: lasts few days-weeks, last much longer if conditions aren’t right. Cocoon protects flea in development.

  Adult fleas: emerge from pupae when it senses a host, live for 2-3 months but can last much longer in favourable conditions.
• Treatment of fleas

  Sprays, powders, tablets, shampoos.

  Vacuum and clean and treat environment
• Prevention of fleas

  Using tablets, collars, shampoos and sprays that contain ingredients toxic for fleas
• What are Ticks

  Move from one host to another and feed of hosts blood
• Symptoms of ticks

  Itching

  Skin Irritation

  Loss of fur

  Dull coat
• Lifecycle of ticks

  Egg: hatches in few weeks

  Larvae: Find host to feed on, if they find host the take several weeks- months to develop into nymphs

  Nymphs: require another host to feed and develop in several weeks

  Adults: Once fed enough they mate and die
• Treatment of ticks

  Sprays, powders, tablets, collars and shampoos.

  Also can be removed using special equipment
• Prevention of ticks

  Keeping animal indoors and restricting movement outside

  Higher risk environments like grassy area and wooded/vegetated areas.
• What are mites?

  Similar to ticks but tend to be smaller, feed in organic material or hosts blood.

  Either live on surface or burrow just underneath.

  Less common from mites to carry diseases
• Symptoms for mites

  Itchiness

  Sore/dry skin

  Dark crusts of skin in ears

  Poor condition
• Lifecycle of mites

  Eggs

  Larvae hatch from eggs- 3 legs

  Nymph

  Adult- 4 legs

  Life cycle varies across 2-4 weeks
• Treatment of mites

  Chemicals that kill mites and ticks called acaricides and are available in sprays, dips, shampoos etc.
• Prevention of mites

  Keeping bedding and environment clean

  Separating infected animals