Rooiluise By Angorabokke

RED LICE  /Rooiluise (SIEN AFRIKAANS ONDERAAN)

Red Lice ( Damalinia limbata /Bovicola limbata) adversely affects mohair production.

Damalinia limbata (red / biting lice)

Red lice occurrence and time of year (L Brown, T C de K van der Linde, L J Fourie and I G Horak).

The study found:

• Adult biting lice Damalinia limbata were most numerous on Angora goats from November to May with the smallest numbers present during August (shearing in July).
• Nymphs were most numerous from January to March with the smallest numbers present during July.
• This finding corresponds to Angora goat kids on irrigated pastures and on 18-month-old Angora goats in the southern Karoo in which peak numbers of D. limbata were recorded during March.
• The decrease in numbers of limbata after shearing agrees with findings on Angora goats in the southern Karoo.
• The ventral surface of goats has the highest average temperature during winter compared with other body regions and the largest proportion of adult lice was present here during this season when their populations were at their lowest.

Causes reducing lice numbers include:

• Shearing
• Solar radiation
• Increased relative humidity (thunderstorms) lead to reduced fecundity by female lice and reduced nymphs.
• Decreased temperatures also leads to reduced lice fecundity and hence reduced nymphs in Autum while adult levels drop later in winter as they die of old age.

Effect on body mass

Infestation did not affect the body weight of goats

Effect on Mohair

Lice adversely affected both the quantity and quality of mohair produced. At the commencement of the study the average weight of mohair produced by goats in the 2 groups differed by only 5 g.

During the 6 months after treatment (Pyrethrin) the goats in the treated group produced an average of 271 g more mohair per animal than those in the untreated group.

When the mohair clips of the 2 groups were classed it was found that the treated goats produced better quality cuts with less damage to the hair than the untreated animals It is suggested that changes quality are indirect and result from the irritation caused by lice, which elicit host responses such as rubbing, scratching and biting. However, lice also cause the skin to thicken, and a decrease in production due to alterations in the skin structure.

Red lice preference for the Angora goat.

An adult Angora goat ewe was kept with an adult Boer goat ewe in a pen of ten by nine metres for seven months. Red lice on the Angora goat ewe never parasitised the Boer goat ewe and at the end of this period she had no lice on her skin. (J Joubert)

Survival of red lice away from the Angora goat

At the Veterinary Laboratory in Middelburg, a trial was done which showed that adult red lice can survive away from the Angora goat for only 36 hours under optimum environmental conditions.

TREATMENT

Treatment- The importance of knowing the life cycle of lice.                       

Due to the fact that:

• Eggs hatch 9-12 days after being laid
• A laid egg takes as little as 3 weeks to develop into an adult in optimum conditions
• MOST treatments are NOT OVICIDAL (that is don’t kill the eggs)

This is often the reason that the red lice are ‘back’ a month after treatment and why treatment as directed by the manufacturer must be followed. (Usually requires a second treatment after 2 weeks)

• Organophosphate and Pyrethroid dips should not be used within 3 months of shearing so that the mohair clip is not contaminated

SEE list of treatment options under DRUGS - ECTOPARASITE DRUG LIST

RESISTANCE DEVELOPMENT

Mohair producers in South Africa have expressed concern at the apparent increase in the prevalence of biting lice on their goats, and it has been suggested that this could be due to the development of resistance to insecticides. However, it would seem that in some cases in which a perceived breakdown in product performance has been reported, the problem was due to incorrect usage.

The resistance of lice to insecticides is an inherited phenomenon. It results from exposure of populations of lice to chemical insecticides and survival and reproduction of lice that are less affected by the insecticide. As obligate parasites, opportunities for refugia of lice tend to be more limited than in parasites with an extended free-living phase.

 Action by the farmer to reduce resistance:

• The simultaneous use of two or more parasiticides with different mechanisms of action or different target site effects can be an important strategy in maintaining a low level of resistance. (Hennessey and Andrew, 1997).
• The product label instructions must be followed closely. If the label states two treatments, then two treatments must be administered. The first treatment will only kill active stages of parasites present on the sheep at the time of treatment. The second treatment will kill any eggs that have hatched since the first treatment. Taking care to apply topical insecticide formulations directly along the backline immediately after shearing will maximize the even diffusion of active ingredients around sheep flanks, thereby contacting lice inhabiting sites remote from the point of drug application (Finney, 1971).
• Rotation/alternation of different classes of parasiticide
• All oncoming stock should be quarantined for at least three weeks (21 days), and observed for signs of infestation. Do not mix with the main flock until treatment is complete and the parasite eradicated. In an area where resistance has occurred, continued use of a pesticide may be required to control other parasites that remain susceptible.
• The excessive use of parasiticides for short-term gains may be the worst possible practice in the long term (Hennessey and Andrew, 1997).Fewer applications, which reduce the selection pressure over time, would decrease the rate and probability of resistance development
• ‘Good Dipping Practice’ should be followed. Saturation dipping must be carried out. Heads must be submerged at least twice. Goat rams with long horns that do not have their heads submerged may carry lice populations causing re-infestation. Just one incorrectly dipped goat can be a source of infection.
• Farmers often do not having a measuring jugs to correctly determine the concentration of the dip. Too weak a dip mixture will lead to more rapid resistance development. Calibrated dip tanks with known volumes and dip made up accordingly.
• Note that initial filling of dip tank and replenishment concentrations may be different. Length of hair may also determine the manufacturers dipping concentration.
• Farmers often make the mistake of only re-filling the dip tank when the levels get a bit low rather than constant rate replenishment. (The active ingredient gets  ‘stripped’  by the hair from the dip concentration while dipping)
• The mistake is often made of adding ‘a bit of dip’ when dipping to clean mohair before shearing. Understrength dip ensures rapid development of resistance.
• Do not use unlicensed dips such as pyrethroids used for citrus trees.

(Ref: ftp://ftp.fao.org/docrep/fao/010/ag014e/ag014e09.pdf)

ROOILUISE BY ANGORABOKKE (Dr MacFarlane)

Die voorkoms van rooiluise  onder angorabokke is deesdae dramaties hoër. Die probleem is nou moeiliker om te beheer omdat die luise al ’n weerstand teen die organofosfate en paratiroïed dipmiddels en ander produkte op die mark opgebou het.

Die verliese in ons bedryf is groot, aangesien rooiluise die gasheerdier irriteer, wat hom laat krap, wat op sy beurt die haar beskadig, en gevolglik die haargehalte sowel as die prestasie van die bokke nadelig raak.

Rooiluise kan maklik gesien word, met die blote oog, as ’n mens net reg kyk. Hulle is beweeglik, rooierig van kleur en sowat2 mm lank.

Moenie rooiluise met blouluise of die jong larwes of nimfe  wat aan die vel sit verwar nie.Dié probleem moet egter ook aangespreek word, aangesien hulle die diere se kondisie erg kan laat verswak. Laasgenoemde is taamlik maklik om te beheer, omdat die meeste geregistreerde dipstowwe nog werk vir hulle.

Om die probleem doeltreffend aan te spreek moet ’n mens presies dieselfde doen vir rooiluise as wat jy sou doen as jy brandsiekte van jou plaas af wil weer. Dit beteken – 

• dat jou heinings hulle doel goed moet dien, sodat diere van buurplase nie by jou diere kan uitkom nie; en
• dat alle bokke (pasgebore bokkies ingesluit) tegelykertyd behandel moet word. Al slaan jy net een besmette dier oor kan dit nog steeds die hele oefening in die wiele ry.

Luise is uiters gasheerspesifiek. Die rooiluise op bokke is nie dieselfde spesie as dié op skape of ander diere nie.

1. Wanneer jy dip is van kritieke belang. Die beste tyd is 2 tot 6 weke ná die diere geskeer is, wanneer die haar nog kort is en wonde genees het.
2. Al die diere moet behoorlik gedip word, in ’n gepaste dompeldip, en moet minstens twee keer heeltemal ondergedompel word aangesien die luise om die basis van die horings en om die ore aan die lewe kan bly as die dier nie behoorlik gedip word nie. Die bokke moet ± 9 meter swem.
3. Daar moet elke keer vars dip aangemaak word en die dip moet op volsterkte gehou word:
4. Al die bokke op jou eiendom moet tegelykertyd behandel word.
5. As daar enige nuwe bokke op die plaas aankom, moet hulle dadelik geïsoleer en behandel word, en drie maande onder kwarantyn wees. Hulle word ná die drie maande deurgekyk en miskien weer behandel voor hulle deel van die kudde kan word.
6. Skoudiere kan by ander diere luise kry en moet behandel word wanneer hulle terug is.
7. Vervangingsdiere moet nét uit skoon kuddes aangekoop word.
8. Luise kan ook deur skeerders van een plaas na die ander oorgedra word. As die skeerders so pas op ’n ander boer se plaas klaargeskeer het, moet hulle by hul aankoms skoon oorpakke kry.

As jy bostaande maatreëls toepas loop jy ’n baie kleiner risiko dat jou diere  weer luise kry. Dit mag selfs moontlik wees om die luise geheel en al uit te roei.

Dit wat meer verdien omdat jou bokhaar van ’n beter gehalte is, behoort genoeg te wees om jou te vergoed vir die finansiëlem en bestuursinsette wat nodig is om rooiluise onder ons nasionale kudde te beheer.