A LABORATORY METHOD FOR THE REARING OF DERMANYSSUS GALLINAE (DEGEER, 1778) (ACARI, DERMANYSSIDAE)ABSTRACT
The present paper describes a laboratory method for the maintenance and feeding of D. gallinae colonies. The colonies were kept in Pasteur type disposable glass pipettes, with the wider extremity sealed with a nylon mesh screen. After the placement of the mites into the pipette, the narrower extremity was fire-sealed in a Bunsen bumer. For colony feeding a restrained chick was placed in a plastic basket, with its bottom covered with paper towel, containing in the top border, in the outside, a twisted strip of paper, which served as shelter for the fed mites. The basket was placed in a tray containing water and liquid detergent, to prevent the mites from escaping. Among the substances tested as barriers (mineral oil, liquid vaseline, and water), water containing liquid detergent was the most efficient, not allowing the mites to escape. The colony was fed at weekly intervals, the mites being put to feed in the afternoon, and being removed the next morning.
KEY WORDS:
Dermanyssus gallinae
; rearing methods; fowl mite; laboratory rearing
RESUMO
O presente trabalho descreve método de laboratório para criação, manutenção e alimentação de colônias de D. gallinae. As colônias foram mantidas em pipetasde vidro, tipo Pasteur, fechadas com tela de nylon, abertura de malha de 50µm na extremidade mais larga. Após a introdução dos ácaros na pipeta, a extremidade mais fina foi fechada em bico de Bunsen. Para a alimentação da colônia, uma ave imobilizada foi colocada em um cesto de plástico forrado no fundo com papel toalha, contendo na extremidade superior, externamente, uma tira de papel torcido para servir de abrigo aos ácaros alimentados. O cesto foi colocado dentro de uma bandeja contendo água com detergente líquido, para evitar a fuga dos ácaros. Dentre as substâncias testadas como barreira (óleo mineral, vaselina líquida e água) a água com detergente líquido foi amais eficiente, não permitindo a fuga de ácaros. A colônia foi alimentada sernanalmente, êolocando-se os ácaros para se alimentar à tarde e recuperando-os na manhã do dia seguinte.
PALAVRAS-CHAVE:
Dermanyssus gallinae
; método decriação; ácaro degalinha; criação em laboratório
INTRODUCTION
Dermanyssus gallinae is the main mite species that parasitizes layer chickens in the State of São Paulo, Brazil (TUCCI et al., 1997). Among the problems caused to the chicken' s health, anaemia and stress are considered to be the major factors responsible for the drop in egg production.
For the accomplishment of studies on the biology, ecology, physiology and control, laboratory rearing and maintenance of colonies are necessary.
The existing literature recommends the rearing of D. gallinae in boxes, jars and buckets, made with various materiais, where thechickis eitherpermanently restrained or introduced at regular intervals to serve as source of food to the mites.
WISSEMAN & SULKIN (1947) proposed the use of glass bottles, where the chick was placed to feed the mites. They commented thathighmoisture condensation occurred, making it necessary to use, for several time , a fan at the bottle mouth to remove moisture.
CHAMBERLAIN & SIKES (1950) built a metal box, with straw covering the bottom and pieces of corrugated paper serving as shelter for the mites. The chick remained inside the box or was placed inside it twice weekly to-feed the mites. The box had a ditchlike device around it, filled with mineral oil to prevent the mites ftom escaping. The authors describe also that the box had a lid to prevent the chick ftom leaving the box and to keep insects out.
CAMIN & EHRLICH (1960) built two m tal cages, one triangle-shaped and theotherround-shapM, placed one inside the other. The chick remained inside the cage, being removed forcleaning the bottom of thecage only. To prevent the escape of the mites, watet was used as a barrier.
HAMANN et al. (1994), in studies on the biological cycle ofDermanyssus gallinae, used plastic buckets, with lids, and fitted with holes it1 the lateral walls and lid. A wire grid was placed at the bottom 1 and chick feeders were placed in the outside of the bucket to feed the chick which remained inside the bucket
One of the main problems posed qy these rearing methods is related to cage cleaning, that may eliminate large quantities of the parasites. The difficulty to build these rearing places and theit cost also restrict theit widespread use.
KIRKWOOD (1971) developed a device for "in vitro'' feeding of Dermanyssus gallinae. Chick skin and blood were used, reaching a maximum of 70% success in parasite feeding. He comments that more studies are necessary, including the observation of more mite generations, before using the device in experiments.
The only effective way to breed these parasites is through feeding on the host and the difficulties involved in therearing, feeding, recoverirtg and maintaining of the colonies atthelaboratory led totherealization of thiswork.
MATERIALS AND METHODS
Pipettes - The mite colonies were maintaitted itt Pasteur-like disposable glass pipettes, with a wider diameter of 1,5cm anda length of 20 cm. A 50µm mesh nylon screen was sticked to the Wider extremity with a transparent ultra-fast drying glue, The mites were aspirated into the pipette, enotlgh to fill 1/3 of its capacity. Afterwards the narrow extremity was sealed in a Bunsen burner. In the field the aspiration was made with a battery-powered portable aspirator, and at the laboratory the recovery was made by aspiration with the aid of a mouth protector.
Colony feeding - The mites wete placed to feed, once weekly, on a 7 to 25-day-old chick (Gallus gallus domesticus). The container used to restrain the chick was a plastic basket, similar to those used for garbage in kitchens, 24cm high and with a wider diameter of 20cm, withoutlid(Fig.1). Extetnally, astripoftwisted papet towel was sticked with adhesive tape to the top border of the basket, surrounding it, so that the mites, after feeding, could shelterin that place. Internally, the bottom of the basket was covered with paper towel to absorb feces. Aiming to prevent the chick from destroying the parasites, its feet were tied with a strap so thatit could walk butnot scratch itself. On the chick's head was placed a plastic coffee cup, with the bottom cut off to allow the head to pass, so that the chick could moveitsheadbutnotpeckitsbodytoeatthemites. The chick and the pipette containing the mites were then placed in the basket and the nylon mesh screen seal of the pipette ruptured, To ptevent thechick from escaping the basket was covered with a sheet of paper, sticked into place with adhesive tape. Then the basket was placed onto a plastic tray containing water and liquid detergent to prevent the tnites from escaping. The parasites were put to feed at 6 o' clock in the evening and removed at 8 o' clock in the following morning.
Mite removal
The removal of the mites was accomplished by the withdrawal of the twisted paper from the basket and its placement on a white tray. Then a 20 centimeter-long strip of the paper was cut and the mites which agglomerated there were aspirated into a new pipette. After all the mites were captured another, 20 cm strip was .cut, and the sarne process was repeated. The mites that escaped were easily seen on the white tray, because of th irreddish calor. After the recovery, the chick and the paper towel from the bottom of the basket were also examined, and the remaining rnites were aspirated. The narrow extremity of the pipette was fire-sealed in with the aid of aBunsen burner and stored in an incubator at 25ºC with 70 to 80% relative humidity. In spite of feeding preferably at night, some mites might yet remain on the body of the chick; some might remain on the bottom of the basket, among the feces of the animal. Then, the chick and the paper towel from the bottom of the basket were examined and the mites which were found were aspirated. At the end of this procedure all used material was heated in an oven for one hour at 80ºC. The chick was either bathed in an acaricide solution ordiscarded.
Substances used as barriers.
Four different substances were testedforuse as barriers: pure water, water contairiing liquid detergent, mineral oil and liquid vaseline. The tests were done while the parasites were feeding and also by plàcing the mites on these substances and observing if they did or did not escape.
RESULTS ANO DISCUSSION
The method employed here proved very effective in the maintenance of D. gallinae colonies in the laboratory, with the occurrence of a great increase from the initial population, and including the advantages of keeping a large number of colonies in small room spaces, and avoiding the risk of contamination among them.
It was observed that, with the useof disposable glass pipettes to serve as shelter for the parasites after feeding, the risk of escaping is negligible, provided that the nylon mesh screen is well sticked to the pipette and the glass tightly fire-sealed.
When themites are kept in boxes orother containers, where the chick is placed only to feed them, the risk of losing several specimens is present. This may happen for two reasons: during the cage cleaning and by the escape of the mites. Three days after feeding, most of the blood that was ingested by the mite is digested and it is able to feed again. During the absence of the host the mites wander in a frantic manner at night on the walls of the rearing cage, in search for food. Many of them escape and die in the barrier, thus reducing the number of mites of the colony. Besides that, if the barrier is not effective, there is a risk of the mites escaping out of the rearing cage and infesting, undesirably, otherchicks.
Inrearing cages many mites build theircolonies arnidst the chick feces which accumulates on the bottom of the cage, andduringcleaningmanyparasitesmaybeelirninated together with the excrements from the cage.
Other disadvantage of the systems that keep the chick all the time in contact with the parasites is that the parasite population grows too fast, generating a very large population in a few weeks. It was noticed that the chicks became very debilitated, and when these were substituted for new chicks, these ones died because they could not stand such a great number of parasites. This led to another problem that was dividing the colony into two new systems, which would increase the space required and the costs of rearing.
Among thefour substances tested as barriers, it was observed that pure water and liquid vaseline allowed several mites to escape from the tray, and, particularly in water, the mites quickly reached the border and walked out of the tray. Mineral oil was as effective as water containing liquid detergent, preventing the escaping of the mites, however its use raises the costs of rearing the mites. Water containing liquid detergent was considered the best option. As soon as the mites got in contact with this barrier they sank quickly <1.nd died in the bottom of the tray. Despite that, the ideal is that the mites do not escape to die in the barrier, therefore the system tested here for parasite feeding was very effective. The strip of twisted paper, placed on the top border of the basket, proved to be ao excellent shelter, keeping almost all fed mites.
ACKNOWLEDGMENTS
Silvana D' Agostini for the figure.
REFERENCES
- CAMIN, J.H. & EHRLICH, P.R.A. · A cage for maintaining stock colonies of parasitic mites am1 their hosts. J Parasitol., v.46, p.109-111, 1960.
- CHAMBERLAIN, R.W. & SIKES, R.K. Laboratory rearing methods for three common species ofbird mites. J. Parasitol., v.36, p.461-465, 1950.
- HAMMAN, W.; GRISI, L.; FACCINI, J.L.H.; MASSARD, C.L.; FALCE, H.C. Observações sobre o ciclo biológico doDermanyssus gallinae (De Geer, 1778) e do Ornithonyssus sylviarum (Canestrini e Fanzago, 1887) (ACARI: DERMANYSSIDAE). Agrárias,Curitiba, v.13,, n.1/2, p.99-103, 1994.
- KIRKWOOD, A.C. In vitro feeding ofDermanyssus gallinae. Exp. Parasito/., v.29, p.1-6, 1971.
- TUCCI, E.C.; GUIMARÃES, J.H.; BRUNO, T.V.; GAMA, N.M.S.Q.;SANTQS, A.M.M. Ocorrência de ácaros hematófagos e·m aviários de postura no Estado de São Paulo, Brasil. Rev. Eras. Parasitol. Vet., v.5, n.2, 1997. (in press)
- WISSEMAN JR., C.L. & SULKIN, S.E. Observations on the laboratory care., life cicle, and hosts of the chicken mite, Dermanyssus gallinae. Am.J.Trop.Med., v.27, p.463-469, 1947.
