Parasites and Vaccines

Ixodes holocyclus - environment, life cycle, identification

• found in coastal QLD, NSW north Vic

• prefers warm, and humid weather = Spring-Summer

• Host = kangaroos, bandicoots, koalas, possums

• only female ticks infect

  • lay eggs in grass → hatch in 18-28 degrees → 1st host → jump off and grow → 2nd host (become male/female) → 3rd host (only females) → produce toxins on final host → jump off (males then feed off females)

• Identification

  • 8 legs clustered at the front of body (1st + 4th leg is darker)

  • anal groove

  • colours vary but often grey

Ixodes holocyclus - where and how does it effect host

• found on head and neck of patients (looking for CO2)

  • most likely in skin folds = prepuce, toes, ear canals, trachea

• takes 5-7 days from attachment → clinical signs → death in 24-36 hrs

  • can’t tell how long the tick has been on host

  • only x1 tick to kill host → find it and remove asap

  • ticks can’t live without heads

  • will create tick craters, left once tick is removed

• Ixodes holocyclus produce neurotoxin → ascending muscle paralysis

  • block acetylcholine → release presynaptic neuromuscular junctions

Ixodes holocyclus - clinical signs for host

• Ascending paralysis

  • hind limb → tetraparesis (all limbs → wobbly gait)

  • palpebral (blink) or change in pupil size

  • gag reflex and regurgitation → aspiration pneumonia (death)

  • megaoesophagus (sloppy)

  • altered voice (more in cats than dogs)

  • unable to urinate

  • respiratory paralysis (increased effort/coughing → can’t breath = death)

7 Key effected areas = “Little Bugs Like Stopping Our Little Babies”

• legs, bladder, lungs, stomach, oesophagus, larynx, blink

Tick paralysis diagnostics and disease progression

Diagnosis

• no actual diagnostic test

• clinical signs + tick on pet (may fall off)

• rule out other diseases → spinal, GIT, snake venom (bloods to rule out)

• response to treatment → antiserum or tick prevention

Disease Progression

• 5-7 days

• Tick Severity scoring = based on weakness (1-4) and respiratory (A-C)

• If found tick → monitor closely for 24-48 hours

• if in doubt, use antiserum

General treatment of the tick paraysis patient

Sedation

• stress → increased RR = increased O2 demand + fatigue

• stress → increased risk of regurg/vomit → aspiration pneumonia

Remove tick

• removal method does not change outcome - just get it out!

• tick clip can help finding others (sedate) - every 4 hours

• acaricide spray/bath

Tick antiserum

• antiserum = stop symptoms getting worse by neutralise toxins in blood

• hyperimmune serum made from canine plasma

• slow IV, dilute 50:50 w saline to increase safety, monitor for reaction

• if reaction = stop transfusion + fluid bolus ± antihistamines/adrenaline

Oxygen

• precaution to avoid hypoxemia (resp paralysis, aspiration pneumonia)

• measure with SPO2 (MM + blood), and arterial blood gas

• flow by O2, mask, nasal or O2 cage → if severe ventilator

Hydration

• no food or drink to protect airways (can go no food 5-7 days)

• IV fluid therapy only - maintenance rates only but watch for overload

Antinausea medications

• prevent aspiration pneumonia + monitor, keep head elevated,

Ocular Care

• unable to blink due to facial nerve paralysis

• common to develop corneal ulcers and bacterial infections

  • stain uptake = antibiotic ointment + lubricate

  • no stain = prevention + lubricate

Bladder Care

• urinary retention due to paralysis

• can manual expression or urinary catheter

• ultrasound after urination to ensure complete emptying

• measure urine in bag = total volume / patient weight / time (mls/kg/hr)

Ventilation

• if severe muscle fatigue (low O2, high CO2) paralysis/ aspiration pneumonia

• intense nursing care

• if ventilation required, at least 1- 7 days with 75% survival rate

Treatment / hospitalisation of Tick Patient

• in hospital for 1-14 days

  • depends on = response to treatment, severity, secondary complications, owner finance

• Tick grade = don’t not correspond to prognosis

  • tick clip to allow thorough search

  • tick anti-toxin serum

  • sedation

  • antibiotics

  • O2 support or mechanical ventilation

• Animals will die from

  • respiration fatigue

  • aspiration pneumonia

  • lack of money for supportive care

• Nursing

  • quiet, limited lights, limited people sedation

  • reduce stress

  • ideally sternal, but often recumbent - change position every 4hrs to prevent atrophy and lung collapse

  • soft bedding

  • if regurgitating or vomiting, keep larynx high w head down

• Physio

  • passive range of motion

  • every 4-6 hours for 10-15 minutes

  • stop if increased stress

When can you discharge a tick patient + prevention?

• must be able to stand and ideally walking

• have a gag relfex and able to eat as normal

  • try water trial first → soft food

  • monitor closely to avoid vomiting and regurgitation

• able to urinate

• discharge with instructions - strict rest

Prevention

• oral chews and tablets or spot on to prevent

• manual visual tick search is best

Where is heartworm found - host and environment

• dogs are natural hosts but wild variations (dingos) that limits us from eradication, also zoonotic

• found in east coast of Australia

• only 20% of dogs show clinical signs (resp, lethargy, right sided heart failure) = ideally prevent

• Environment

  • natural disasters

  • changes in natural climate conditions

  • online adoption → pet transport

  • pet owners travelling in infected areas

  • non-compliance w medications

  • 60 species of mosquitos are known vectors

Lifecyle of Dirofilaria Immitis (Heat worm)

• Microfilariae (young heartworm) and antigen detectable in blood by 180 days - 9 months post infection

• L1 → L2 → L3 (2 weeks in mozzie - intermediate host)

• L3 use proboscis to inject → create hole → migrate to heart/lungs

• L4 = prevention products target larvae

  • topical or oral every month, mixed dose = reduced efficacy

  • Proheart = every 12 month INJ (previous 3months also)

• Immature adults

• Adult = 6 months will produce antigens and microfilaria

  • survive in pulmonary vessels for 90-120 days

  • live in heart and lungs for 7 years if untreated

  • 30cm in length

  • can be found on radiograph and ultrasound

  • damage pulmonary vessels

  • proliferation and inflammation of vessels → scaring

  • permeant damage - occurs before antigen tests are positive

How do you test for Heartworm and what are the benefits?

Tests	Benefits
Microfilaria Microscope blood sample Knotts test - large volumes of blood PCR live parasites in buffy coat	confirm antigen result know if they has or will be a transmissional risk if untreated know if they may react to milbemycin prevention microfilaria need to be monitered and cleared
Adults antigen tests higher sensitivity for females lower sensitivity for males highly specific but not 100%	eassurance that current prevention is effective limits ongoing transmission to other animals early detection = easier to treat + better prognosis negative for adults positive for microfilaria support screening for resistance to preventative drugs long term financial gain

Reasons for false negative/positive results for adult heartworm tests

False-Negative Result	False-Positives Results
low worm numbers antigen already bound to antibody in dog, before being put in the kit males have lower sensitivity than females low antigen level in blood anti-microfilaraemia infections too young (only detectable at 5-9 months) ML preventatives not killed yet (slow)	cross-reactivity w other parasites infection in other parts of body (ectopic) recent preventative treatment = antigen in blood still blood transfusion contains antibodies unknown reasons

Reasons for positive or negative results when testing microfilaria

Positive	Negative
both microfilaria and adult heartworm antigens present microfilaria positive, but antigen negative (antigen-antigen binding) microfilaria positive, but antigen negative (adults died) blood transfusion with microfilaria placental transfer with microfilaria False-Positive = incorrect parasite detected	both microfilaria and adult heartworm antigens negative antigen positive, but microfilaria negative single sex infection not enough blood to examine microfilaria killed by preventative drugs

Heartworm Preventative

• daily tablets = inconvenient and forgotten

• monthly product = available everywhere, sometimes forgotten, can be misinterpreted with what is required

• annual injection = 100% compliance as vet is in control (ProHeart)

Preventatives = Macrocyclic Lactones (ML’s)

• Avermectins

  • Selamectin = Revolution

  • Ivermectin = HeartGard or Exelpet

• Milbemycin

  • Moxidectin = ProHeart INJ, Advocate, Simparica,

    • gold standard, broad spectrum

    • protects from birth + can be taylored for vaccination and desexing protocols

    • best compliance

  • Milbemycin Oxime = NexGaurd, Sentinel, Comfortis Plus

Roundworm Lifecycle

• dogs and cats → pot belly

• ingest infected eggs from soil OR eat secondary host OR in utero OR via milk from mother

• Pre-patent period = 2-4 weeks

• adult worms life in small intestine

  • Clinical signs = pot belly, but also weight loss, dull coat, vomiting, intestinal obstruction

  • is zoonotic → visceral and ocular larval infection

• eggs passes in faeces and develop over 1-4 weeks in environment

Hookworm Lifecycle

• dogs and cats (most common worm) but mostly puppies → anaemia

• ingest larvae from soil OR in utero OR via milk from mother OR worms burrow into skin

• Pre-patent period = 2-4 weeks

• adult worms life in small intestine

  • Clinical signs = severe blood loss → anaemia, blood diarrhoea, vomiting, weight loss

  • Is zoonotic → gut infection and cutaneous larval infection

• eggs pass in faeces

Whipworm Lifecycle

• only dogs (rare) → straining + blood in diarrhoea

• ingest infected eggs from soil

• Pre-patent period = 10-12 weeks

• adult worms life in caecum

  • Clinical signs = straining to defecate, bloody/mucoid diarrhoea,

  • not zoonotic

• eggs pass in faeces

Tapeworm Lifecycle

• dogs and cats → anal irritation / scooting

• ingest flea larvae during grooming

• Pre-patent period = 2-3 weeks

• tapeworms within the flea will develop to adult tapeworms in small intestine

  • Clinical signs = anal irritation → scooting, segments of worms in faeces

  • is zoonotic → very minor signs

• eggs pass in faeces

Types of Tapeworm

• Flea tapeworm

• Taenia tapeworm = rodents intermediate → livestock

• Hydatid tapeworm = uncooked meat/organs of intermediate → dogs

  • Hydatids = fluid cyst in liver or lungs of sheep, cattle, people

  • Sheep measles = cyst in sheep muscle from dog tapeworm

  • Bladder worms = large cyst in liver/abdomen of sheep from dog tapeworm

Giardia Lifecycle

• dogs and cats → diarrhoea

• ingest cyst from environment / contaminated water

• trophozoites emerge from cyst and attach to mucosa of small intestine

  • Clinical signs = diarrhoea

• trophozoite create cysts and pass in faeces

• ONLY treat Giardia if animal is showing clinical signs!

How do you diagnose and treat internal parasites?

• Vetscan Imagyst = new microscope equipment than analysis sample and identifies intestinal parasites / eggs

• Faecal float

• Clinical signs

Treatment - all product specific

• Hookworm and Roundworm = 2, 4, 8, 12 weeks, monthly till months, then every 3 months. Before and after pregnancy

• Whipworm = 6-8 weeks after 3 months old

• Tapeworms = every 3 months

• Hydatid Tapeworm = every 6 weeks

• Giardia = only treat if infected, treat for 3 consecutive days

Fleas Lifecycle and Characteristics

• dogs and cats → itching on back, pelvis, tail = anaemia

• eggs (50%) hatch into larvae in environment within 2-5 days

• larvae (35%) feed for 5-21 days on adult flea faeces / debris in environment

• pupae (10%) develop inside a debris coated silk fibre cocoon

• adult fleas (5%)

  • emerge from cocoon after 3-28 days

  • feed on blood host = microliters of blood daily = anaemia

  • mating occurs within 8-12 hours

  • produce 20 eggs per day = 5000 eggs in life

Characteristics

• wingless, laterally flattened with backward projecting spines

• move quickly in hair + can jump up to 35 cm

• stimulated by physical pressure, CO2 and heat

• seek light and move up hair / immediately seek host + feed

Ticks Lifecyle

• dogs, cats, humans → anaemia or paralysis

  • Paralysis tick, Bush Tick or Brown Dog Tick

• Eggs hatch

• Larvae attach to 1st host = small mammal (rodent)

• Larvae falls off and becomes a Nymph

• Nymph attach to 2nd host = small mammal, dog, cat, human

• Nymph falls off and becomes a Adult

• Adult attach to 3rd host = mammal, dog, cat, human

  • females engorge and feed off blood → produce toxin

  • lay eggs

Prevention = up to date with tick prevention, checked daily, clincial signs

Ear Mites (Otodectes cynotis)

• dogs and cats (mainly younger) → itchy ears

• contagious, spread via contact

• causes ear infestation = canal inflammation, redness, swelling

• clinical signs =

  • brown waxy/crumbly discharge from ears

  • pruritis/ itchy

  • secondary self trauma and yeast or bacterial infections

Demodex Canis Mites (Mange)

• just dogs, all ages → patchy hair loss or disease

• infected by close contact from infested mother

• live and reproduce in hair follicle and sebaceous glands

• dogs are predisposed if = specific genetics or immune disorders

• all dogs have low numbers of mites

• Signs =

  • patchy hair loss

  • thickened and pustular skin

  • can have secondary infections of pruritis

  • lead to life threatening disease

Sarcoptes scabiei Mites (Mange)

• dogs and cats - very itchy skin

• tunnel into skin → intense itching → alopecia

  • usually start at elbow or ear but can travel to ventrum

• highly contagious, spread via contact to dogs, cats and humans

  • if one animal has it, treat all before they develop signs

  • humans will resolve spontaneously in 12-14 days

Define vaccines and herd immunity

Vaccines

• critical to health and welfare

• apart of annual visit

• educate about preventative health = aid early disease detection

• individualised protocol

• develop immunity to disease to reduce side effects at re-exposure

• can have reactions but they are minor and resolve with time

• must be stored cold, and generally not frozen - always record

Herd Immunity

• Herd immunity = level of resistance to the spread of a disease within a population

• high vaccination rates = increased herd immunity = less disease

What vaccines should be given to dogs and cats?

Dog	Cat
Canine Parvovirus (CPV) Canine Distemper (CDV) Canine Infectious Hepatitis (CAV 1 / CAV 2)	Feline Parvovirus (FPV) Feline Herpesvirus (FHV) Feline Feline Calcivirus (FCV)
Canin Parainfluenza (CPi) Bordetella Bronchiseptica (Bp)	Chlamydophila / Chlamydia felis Feline Leukaemia Virus (FeLV)
Leptospirosis Canine Coronavirus (CCoV) Tetanus	Feline Immunodeficiency virus (FIV) - always given solo

Horses = tetanus, strangles, equine herpes, Hendra (+ rotavirus if breeding)

How do you create immunity for disease?

Antigens are foreign substances that stimulate an immune response → develop “protective” immune to the whole or element of pathogen

• Mechanical immunity = physical barriers (skin)

• Non-specific immunity = normal WBC attacking foreign material

• Specific Adaptative immunity = develop with exposure

These all the provide either (ideally both)

• Humoral immunity = antibodies

  • Y shaped proteins that recognise and bind to antigen

  • passive or actively acquired (bodies immune system)

  • extracellular pathogens

  • uses Antigen presenting Cells, helper T cells and B cells to create Plasma and Memory cells

• Cell mediated immunity = WBC that remember

  • cytotoxic T cells that recognise antigens on surface of infected cells and destroys them

  • hard to measure

  • intracellular pathogens

  • uses help T cells and cytotoxic T cells to destroy infection

Both of which then assist in pathogen removal and development of memory cells (boosters) = increased rapid immune response

What is mucosal immunity? Where can you get it?

• IgM = produced briefly in the blood when immune is first exposure

• IgG = long lasting antibodies in blood

• IgE = produced in response to allergies and parasites

• IgD = in humans

• IgA = produced at mucosal surfaces in response to local application of antigens

• INJ vaccines = IgM and IgG = systemic immunity (reduce response)

• Intra nasal + oral vaccines = IgA = mucosal immunity (stop penetration)

Describe Intranasal vs Oral Vaccines

Intra Nasal	Oral
Only used for Canine Infectious Respiratory Disease (Kennel Cough) may need annual boosters	Only used for Canine Infectious Respiratory Disease (Kennel Cough)
Pros single dose (live vaccine) rapid response broader spectrum then INJ induce mucosal immunity Cons not well tolerated limited systemic immunity	Pros single dose (live vaccine) good mucosal immunity convenient + easy Cons narrow spectrum - only Bordatella bronchiseptica

Describe Injectable Live vs Killed Vaccines

Live Vaccines	Killed Vaccines
virus/bacteria is alive in vaccine to induce protective immune response but not capable of causing disease	virus/bacteria is killed before administration. May contain an adjuvant to assist into the stimulation of immune response
Pros rapid + durable less likely to cause SE single dose is effective few boosters needed both humoral and cell-mediated immune response Cons multiply in body some SE cannot be used if pregnant virus/bacteria may shed and interfere with testing good storage / handling “revert to virulence” or combine with wild type viruses	Pros no risk of spread no interference with testing no risk of causing disease no risk of “reversion to virulence” can be given if pregnant stable storage / handling Cons need adjuvants added more likely to cause SE need multiple doses + boosters only humoral responses (not cell mediated)

Considerations for Puppy Vaccines

• maternal antibodies

  • protect young animals

  • last for varying periods

  • but neutralise vaccines → will only respond to vaccine when low number of maternal antibodies left (hard to measure)

• must deliver in the window of susceptibility - hence multiple

  • at 6-8 weeks, then 10-12 weeks, then 16 weeks, then annual

• All core vaccines (C3) need to be delivered before 10-12 weeks

• Wil need annual or tri-annual boosters

• Parvo vaccine covers all 3 strands of parvo virus