Parasites

Question 1

Is anthelmintic resistance a problem in cattle?

Answer 1

yes, but as of right now, we are unsure of the extent. We know that it is not the same level of an issue as it is in small ruminants.
Resistance is reported in all 3 drug groups (MLs, BZs, and nicotonics) but there just are not many people collecting data.

Question 2

What (7) parasites are problematic in immature cattle?

Answer 2

1. cryptosporidium
2. coccidia
3. lice
4. trichostrongyles
5. face fly, horn fly
6. other biting flies and possibly ticks?
7. theileria - emerging

Question 3

what (6) parasites are problematic in cows?

Answer 3

1. face flies, horn flies
2. other biting flies and ticks?
3. lice
4. trichostrongyles
5. theileria
6. chorioptes

Question 4

what (6) parasites are problematic in bulls?

Answer 4

1. face flies, horn flies
2. other biting flies
3. lice
4. trichostrongyles
5. tritrichomonas
6. chorioptes

Question 5

What is the common complaint / signalment in cattle that are suffering from high parasite burdens?

Answer 5

poor-doing weaned calves/stockers/heifers

Question 6

Adult trichostrongyles live in the _____________.

Answer 6

GI tract

eggs are passed in manure, then the larvae develop to L3 in 5-7d (depending on temperature and moisture levels). Adults will begin egg-laying in 3 weeks.

Question 7

which trichostrongyles are important in cattle?

Answer 7

1. ostertagia
2. cooperia

there are others that contribute to gastroenteritis but they are rarely the primary pathogen present.

Question 8

T/F: cooperia spp. are found in the small intestine of cattle and are highly pathogenic.

Answer 8

false – they are generally not highly pathogenic.

Question 9

T/F: most strongylid eggs in the manure of young cattle are ostertagia

Answer 9

false – they are cooperia
this is why we dont use fecal egg counts in cattle

Question 10

Which parasite requires much higher levels of macrocyclic lactones than ostertagia do?

Answer 10

cooperia spp.

Question 11

Why are trichostrongyles of GREATEST importance in young cattle (1st and 2nd calf cows)?

Answer 11

because immunity develops over several years.
Subclinical infections characterized by decreased weight gain and growth are common.

When clinically affected, they experience diarrhea, weight loss, unthriftiness, and hypoproteinemia (bottle jaw)

Question 12

what 3 drug groups are used the most?

Answer 12

1. macrocyclic lactones (ivermectin, doramectin, eprinomectin, and moxidectin)
2. benzimidazoles (fenbendazole, albendazole, oxfendazole)
3. nicotinics (levamisole, morantel)

Question 13

why is anthelmintic resistance different for cow-calf operations versus feedlot operations?

Answer 13

because resistance depends on production type and how they manage refugia.
In a feedlot situation, they are not on pasture/not grazing and they just get sent to slaughter, so selection for AR is low. Whereas in a cow-calf operation, these animals are having higher selection for AR and managing refugia is very difficult.

Question 14

why is resistance to macrocyclic lactones are widespread problem?

Answer 14

• heavily used
• pour on convenience
• cheap

Question 15

how do we test for anthelmintic resistance in cattle?

Answer 15

fecal egg count reduction test

1. take fecal egg counts on animals AT time of treatment
2. wait the amount of time for each drug to take effect (ML = 14-21d, BZD = 10-14d)
3. repeat FEC
4. calculate the reduction in FEC

interpretation: 95% reduction = full efficacy; 90-95% = possible resistance; 80-90% = resistance is likely; 80% or lower = resistance highly likely

Question 16

how do we appropriately manage anthelmintic resistance in cattle?

Answer 16

Use combination treatment from different drug groups to get additive effect of the treatments

even if the drugs show decreased efficacy individually, they are showing effective as a combo therapy.

Question 17

which route of adminstration for anthelmintics is MOST effective?

Answer 17

oral administration – some drug will remain in the GI tract, remainder will reach the worms systemically

for pour-on administration, there is much more variability in efficacy and persistence of the drug. there is more potentialy for animals to have subtherapeutic levels that can select for resistance.

Question 18

which anthelmintics select more rapidly for resistance?

Answer 18

Ones that persist such as Longrange (injectable eprinomectin)

so its recommended NOT to use this year after year as your sole method of control; combo tx is better;

Question 19

For all dewormers, what is the most important factor of management to reduce anthelmintic resistance?

Answer 19

MAINTAIN REFUGIA
- dont deworm all cattle
- minimize treatments when refugia is low
- use targeted selective treatment (treat only portion of animals and leave proportion of animals untreated – selective nontreatment)

Question 20

T/F: using targeted selective treatment, we can utilize FECs and body weight at the start of grazing season to predict which individuals need treatment.

Answer 20

false – FEC and body weight at the start of grazing season are NOT predictive.

the current recommendation is to leave a proportion of animals untreated (10-20%) using selective NON-treatment

Question 21

what tick is the vector for theileria oreintalis?

Answer 21

haemaphysalis longicornis
(asian longhorned tick)
which is a 3-host tick found in Asia, Russia, Australia, and NZ. This tick feeds on just about everything and is active March-Nov.
Infestations are found in large numbers on young, stressed animals around head, ears, eyes, and mouth.

Question 22

what are the 4 most common pesticide products?

Answer 22

1. organophosphates and carbamates (Acetylcholinesterase inhibitors)
2. pyethroids (end in -thrin)
3. macrocyclic lactones
4. insect growth regulators/develop inhibitors