parasite control (mallicote) Flashcards
Goal for young horses
limit parasite burden until young horses develop their immunity
goal for adult horses
minimize disase without inducing a resistance to parasiticides
Major internal parasites
-
small strongyles (Cyathostomes)
- seasonally transmitted
- winter in FL, summer in north
- Large strongyles
- Anoplocephala perfoliata (Tapeworms)
- Ascarids - Parascaris equorum
- year round infection of young horses
Minor internal parasites
- Gastrophilus intestinalis (Bots)
- Habronema muscae, Draschia megastoma (stomach worms)
- Oxyuris equi (Pinworms)
- Strongyles westeri (Threadworms)
- Dictyocaulus arnfieldi (lungworms)
Small strongyles / Cyathostomes
- Most important parasite to manage in adult horses
- Significant concern for resistance in these populations
- prepatent period - minimum 5 weeks
- relatively short period of time
Small strongyles / Cyathostomes
life cycle issues
- larvae migrate in cecum/colon walls for 4-6 weeks
- may encyst for months to years
- mature and encysted cyathostomes are not significant in causing disease if moderate numbers
small strongyles
progression
emergence of larvae =>
Intense inflammation =>
hemorrhage and edema of cecum and colon =>
Colic and diarrhea
Large strongyles
- migrate through abdominal tissues
- liver, pancreas, arteries
- LIve in lume of gut
- long prepatent period (6 months)
- don’t have to treat very often
- CS
- colic, poor growth, weight loss
*we rarely see this parasite (since advent of ivermectin)
Parascaris equorum (roundworms)
- adult horses develop immunity
- eggs persist in environment for years
- deadly for young foals
*only parasite that will be in the small intestine of the horse (others in colon….I think)
Parascaris equorum (roundworms)
progression
- parasite lives in small intestine =>
- lymphatics =>
- lungs =>
- pharynx =>
- small intestine
Parascaris equorum (roundworm)
days to reenter SI
28 days
Parascaris equorum (roundworms)
days to produce eggs
72-80 days
-before you see eggs in fecal
clinical signs of ascarid infection
- coughing
- diarrhea, colic
- pot belly
- rough hair coat
- weight loss
- can’t be diagnosed prior to 80-90 days of infection by fecal float
ascarid resistance
*
Control of ascarids
- control fecal egg count reduction efficacy test
- deworm at 60 days of age (exposure, possibility of ascarids in spite of neg fecal)
- deworm q 60 days (ivermectin) until 8-12 months of age or
- q 30 days (pyrantel/benzimidizole group) until 8-12 months of age
Anoplocephala perfoliata (Tapeworms)
- live at narrow ileo-cecal valve
- spasmodic colic
- intussusceptions
- ileal impactions
- praziquantel
- 1 mg/kg-2.5 mg/kg
- pyrantel
- 13.2 mg/kg
*don’t really see resistance to praziquantel
*intermittantly shed so may not see them on a fecal even if they are infected
Tapeworms
foal deworming
adult deworming
- Foals
- deworm prior to weaning
- Adults
- deworm 1-2 times/year
Gastrophilus intestinalis (botfiles)
- little yellow eggs on legs
- treatment
- remove bots from legs
- Ivermectin or Moxidectin
- cause very few clinical signs
- very susceptible to ivermectin
Habronema, Draschia spp (stomach worms)
- transmitted by stable flies
- no significant internal damage
- cutaneous infections => granulomas (sometimes bx)
- eyes, sheath, ventral midline
- treat with ivermectin
- sometimes plus steroids
*if in their normal spot don’t cause lots of clinical dz
Oxyuris equi (pinworms)
- live in small colon
- female cements eggs to skin of anus
- prepatent period 3.5-5 months
- diagnosis probs
- usually found as adult worms
- difficult to find on fecal float
*tape test around anus good for this
*some resistance to ivermectin…?
DDX for tail rubbing
- pin worms
- dirty gelding sheath
- dirty mare udders
strongyloides westeri (threadworms)
- cause of diarrhea in foals
- 5 days - 4 months
- Infectio via milk
- stress of foaling induces larval activation in dam
- Parasite resides in SI
- Immunity quickly developed (4-5 months)
- prepatent period 5-7 days
*imp DDX for diarrhea in foals
Strongyloides westeri
treatment
- treat mares in late gestation/foaling
- macrocyclic lactones
- treat foals PRN
Lungworms (Dictyocaulus arnfeldi)
-
donkeys the problem
- can harbor with no CS
- Horses exposed parasite via donkeys
- cough
- decreased performance
- Treat with ivermectin
- DX: BAL (eosinophilia or parasites), Fecal (Baermans float-settle to bottom)
Parasites of concern for the adult horse
- Small & Large Strongyles
- Tapeworms
- Gastrophilus
- Oxyuris
Parasites of concern for the juvenile horse
- Ascarids-impaction
- Strongyloides
- Small and Large Strongyles
Refugia
- want to maintain a population of parasites that has not been exposed to parasiticides
- Wild type parasites that have not be exposed to anthelmintic pressures (lack resistance genes)
- Minimal deworming favors survival of ‘wild type’ parasites
New Paradigm
- Resistance as emerging problem
- use fecal egg reduction testint to determine to effective antihelmintics
- treat horses with high FEC
- treat during peak transmission season
Fecal egg counts
- Quantitation of strongyle burden
- < 200 epg (don’t treat)
- 200-500 epg (may not treat)
- > 500 epg (treat)
Fecal egg count reduction test
[(pre-treatment EPG) - (post-treatment EPG)] X 100
samples pre and 10-14 days post deworming
FECRT interpretation
- > 90% for pyrantel and BNZ = good
- 80-90% for Pyrantel and BNZ = suspicious
- < 80% for Pyrantel and BNZ = resistance
- macrocyclic lactones < 98% = resistance
deworming
new paradigm
- south: (85 deg F - death to larvae)
- north: (<45 F - will not support hatching)
Egg reappearance Period
-
expected egg reappearance period
- interval between treatment and resumption of FEC > 200 EPG
- Benzimidazoles - 4 weeks
- Pyrantel salts - 4 weeks
- Ivermectin - 8 weeks
- Moxidectin - 12 weeks
Take home message
- Preserve refugia: deworming least often as possible
- Deworm individuals instead of populations
- keep season in mind
Normal foal behavoir
1-2-3 rule
- sternal recumbency within 2 min of birth
- suckle reflex within 30 minutes
- standing within 60 minutes
- nursing from mare within 120 minutes
*1-2-3 rule => 1 hour to stand; 2 hours to nurse; 3 hours to pass placenta
Physical exam
- first 12-24 hours of life
- systematic
- record
- monitor trends
- detect slow changes
foal temps
- normal 99-102 deg F
- hypothermia common in sick neonates
- unable to adequately cool in very hot climates
- FL
Cardiac auscultation
- HR immediately post partum 40-80 bpm
- inc to 100-120
- 80-100 bpm during week 1
- murmurs
- PDA
- innocent flow mumurs (not cont, discrete, etc)
- ventricular septal defect
Foal mucus membranes
- color, injected (red), yellow, abrasions, evidence of sepsis
- also look at conjuctiva (injected vessels consistent with dystocia)
Respiratory rate/Auscultation
- crackles usually last several hours from birth
- transition from fluid filld to air filled lung
- inc in minute ventilation
- rate x tidal volume
- 80 - 30 breaths/min
- inspiratory and expiratory crackles
- dependent atelectasis
- normal 30-40 breaths/min
Umbilical care
- very important
- dilute chlorahex
- dip several times per day until dry
- No tincture of iodine: toxic to tissues
Enema
- Give in first few hours of life
- fleet enemas
- warm soapy water ok too
- ivory
- Do NOT give repeat enemas
Colostrum
- critical for foal to receive to provide antibodies
- foals need about 2 liters in first 24 hours
- first 2 hours life most critical
- gut closure
Immunoglobulin (IgG)
- Measure IgG at 12-24 hours of age (Snap test)
- if < 800 consider transfusion
- if < 400 definite transfusion
*colostrum replacers NOT USEFUL
Vaccinations and antimicrobials
Newborns
- Tetanus antitoxin
- if mare was not properly vaccinated
- Routine antimicrobials not necessary
- Non-observed birth - risk of sepsis - ok to give ABX
- History of problems on the farm - ok to give ABX
Newborn Check list
- 1-2-3 rule
- Dip umbilicus
- give enema
- DVM exam < 24 hours old
- IgG check between 8-24 hrs of age
- +/- vaccinate/antimicrobials
