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Treatment for mites and lice in the ratby "Matmor" in collaboration with Professor Nils Søli at Norges Veterinærhøgskole (The Norwegian Veterinary College) and the Norwegian Fancy Rat Society (NTF)This is the first part of a survey as published in the Norwegian Fancy Rat society's periodical Gnag, and part II as pre-print. Part III will appear later. Thanks to Sheila Sowter for helping me sort out the "Norwenglish"! The spelling mistakes are my own... |
In a former survey for NTF1 infestations of lice and mites were the most common causes for rat owners to seek veterinary advice. No drug for rats has marketing approval, neither for treating lice, mites, nor other maladies. Considering the seriousness of the side effects, users of NTF’s forum, Råttforum in Sweden and Tamrotten in Denmark were asked to fill in anonymously a net based form with questions about treatment for lice and rats. The form can be seen at http://matmor.info/usoek2.htm (Norwegian version only). The prospective participants were asked to fill in the form regardless of treatment outcome. It was explained that information about treatmens which are safe and effective is just as valuable as information about lack of effect or side effects.
The survey had questions regarding
Nine of 25 replies had information about side effects, two about failed cures.
Two replies to the survey alone represented (>) 150 rats. Both replies concerned Frontline.
Table 1: Drugs recorded in the survey
| Drug | Total | Side effects | Poor effect | |||
|---|---|---|---|---|---|---|
| replies | RCT | % RTC | replies | rats | ||
| Advantage Imidaclopride | 3 | 21 (47) | 5,7 (11,9) [5,3 (11,8)] | 2 | >2 | - |
| Advocate Imidlaclopride and moxidectin | 1 | 12 | 3,2 [3] | 0 | - | - |
| Frontline Fipronil | 6 | >180 | 48,9 [45,5] | 3 | Not stated | 1 |
| Ivomec Ivermectin | 4 | 26 (27) | 7 [6,8] | 2 | >2 | - |
| Stronghold Selamectin | 11 | 129 (>130) | 35 [33] | 2 | 2 | 1 |
As no veterinary drug for rat has a marketing approval there are no officially recommended treatment regimes. Even so the use of fipronil, ivermectin, selamectin, and permethrin to combat lice and mites in the rat has been described in scientific litterature. Concerning permethrin the use of dusting powder cannot be compared to Exspot. The uptake would most certainly be very different. Otherwise the litterature describes the use of drugs with a marketing approval for other species than rat. We did not find any scientific literature about the use of Imidacloprid against lice and mites in the rat. The recommendations are by Florida Rat and Mouse Club of America in collaboration with a vet.
Table 2: Use and reccomended use
| Drug | Confirmed use | Reccomended use | Source |
|---|---|---|---|
| Dosage | Dosage | ||
| Advantage spot-on 100 mg/ml | 1 dr./500 g rat | 1 dr/450 g rat, ½ dr for small rats < 4 months | 2 |
| Advocate spot-on 100 mg/ml + 10 mg/ml | 1 dr./500 g rat | 1 dr/450 g rat, ½ dr for small rats < 4 months | - |
| Exspot* spot-on 744 mg/ml | 0,06 ml adult females 1-2 dr. pups | - | - |
| Frontline spot-on 100 mg/ml | 2 dr./200 g rat | 1 dr/adult rat strength not given but probably spot-on | 9 |
| Frontline spray 2,5 mg/ml | 1 spray (0,5 ml)/250 g or 500 g rat Not stated | 1 spray/rat | 5 |
| Ivomec inj. 10 mg/ml | Not stated | 100-200 µg/lb oral, subcutaneous, or dermal application Dermal: 1 dr. of a solution of 10 mg/ml injection diluted 1+99 in 50% water 50% propylene glycol or 200-400 µg/kg orally, SC or behind the ear after diluting 1+9 with propylene glycol |
2, 3, 8 |
| Ivomec paste horse | 0,5ml/250g rat (1 case), otherwise not stated | pr. 450 g rat: An amount equal to a boiled grain of rice < 450 g rat: equal to ½ boiled grain of rice | 2 |
| Ivomec mixture 0,8 mg/ml sheep | Not stated | oral: 0,125 ml/500g dermal: 0,250 ml/500g
in drinking water : 8 mg/L 24 hours |
2,3 |
| Stronghold spot-on 60 mg/ml (dosage for 120 mg re-calculted as 60 mg) |
1 dr./100 g rat, 2 dr./500 g rat (6 replies without dosage given by weight) | 1 dr./100 g rat, 1 dr. pr. rat | 2,4,6 |
According to the survey, the course of treatment sometimes consisted of one application only of Frontline, Ivomec, or Stronghold. The two drugs for lice and mites for which treatment failed in the survey were Frontline and Stronghold (one report for each remedy). At NTF’s forum treatment failure was reported for Ivomec. In all reports of poor efficacy the treatment was given the recommended number of times according to the listed sources.
Table 3: Number of applications per rat and interval
| Veterinary drug | Survey | Recommendation | |||
|---|---|---|---|---|---|
| No. applications | Interval | No. applications | Interval | Source | |
| Advantage | 2 | 21 d | 1 or more | -/30 d | 2,7* |
| Advocate | 2-3 | 21 d | 1 or more | -/30 d | 7* |
| Exspot | ?(1) | ? | 1 or more | -/7-30 d | 7* |
| Frontline | 1-2 | -/14 d | 1 or more | -/28 d | 5,7* |
| Ivomec | 1-3 | -/10 d | 3 | 7-14 d | 2, 3, 8 |
| Stronghold | 1-3 | 10-21 | 2 or more | 14-30 d | 2, 4 6 |
The case of treatment failure for Frontline applied to the spray, not to the spot-on product. It is possible that the spray dosage is too low to reach the necessary concentration to kill lice and mites when treating large rats, see mg/m2 in table 3. Most likely it is the concentration of the drug in skin fat that kills vermin, not the dose in mg/kg. (Square meter animal has been computed from Meeh’s formula.)
Table 4: Dosage of fipronil 1 spray per rat
| Spray | Rat mg/kg | Rat mg/m2 | Spray | Dog mg/kg | Dog mg/m2 |
|---|---|---|---|---|---|
| 100 g rat | 12,5 | 65,7 | 10 kg dog | 7,5-15 | 161-322 |
| 500 g rat | 2,5 | 22,7 | 60 kg dog | 7,5-15 | 293-585 |
The survey did not report deaths connected to treatment. A search at NTF’s forum showed that in two of the three cases with resulting death, an excessive dose was administered compared to the recommendations in Table 2.
The table below presents all reported side effects, both from the survey and from NTF’s forum.
NB! The number of rats refer to the survey only, not treatment mentioned in forum posts.
Table 5: Side effects of the veterinary drugs
| Veterinary drug | Side effects reported in the survey | Rats with side effects (survey) | Side effects reported on the forum |
|---|---|---|---|
| Advantage (imidacloprid) | Redness, necrosis, nasal noise, tiredness | >2 of 47 | - |
| Advocate (imidacloprid, moksidektin) | - | 0 of 12 | - |
| Frontline (fipronil) | Redness, discolouration, abscess, nasal noise, cramps, imbalance, confusion, agitation, tiredness, poor appetite | ? of 180 | Cramps, death |
| Ivomec (ivermectin) | Redness, hair loss, agitation, tiredness, poor appetite | 2 of 27 | Necrosis, porphyria, imbalance, lethargy, breathing problems, death (acute euthanisation) |
| Stronghold (selamectin) | Nasal noise, discolouration | 2 of 130 | Seborrhoeic eczema |
| Exspot (permethrin) | - | - | Cramps, psychotic behaviour, death |
Side effects from skin and hairs were reported for Advantage (redness and necrosis, one report), Frontline spot-on solution (redness, discolouration, and abscess, one report), Ivomec paste (redness and hair loss one report, overdose), and Stronghold (discolouration one report). At NTF’s forum there was an additional report of a skin reaction to Stronghold: seborrhoeic eczema, and one report of necrosis after the administration of Ivomec injection.
Cramps, imbalance, confusion, and agitation was reported for Frontline spot-on (cramps, imbalance, confusion one report, overdose), for Frontline spray (confusion, agitation one report), and for Ivomec paste (agitation two reports, overdose in at least one report). Additionally cramps, psychotic behaviour, and death was reported on NTF’s forum following administration of Exspot (overdose). Cramps were also reported after administring Frontline spray, dosage unknown. More general side effects like tiredness and a low appetite was reported for Advantage (one report of tiredness), Frontline spot-on (tiredness and poor appetite one report, overdose), and Ivomec paste (tiredness and poor appetite one report, overdose, and lethargy one report).
Nasal noise was reported as side effect in four out of 25 reports. These reports addressed Advantage (two cases), Frontline spray (one case), and Stronghold (one case).