DIAGNOSTIC SERVICES
GENERAL PROCEDURE FOR SUBMISSION OF SPESIMEN
Acari (ticks and mites) which are suspected to be causative agents or vectors of human diseases, may be submitted to the Acarology Unit of IDRC, for identification. Every specimen must be clearly labelled and accompanied by a pathological examination request form. The form must be completed with the following information: brief case history of patient (for clinical specimens), description or identification of non-human host (if any), description of habitat, locality where specimen is collected, date and time of collection, name and address of collector, and date specimen sent to the IMR.
The success of identification depends on the condition of the specimen sent. To ensure success and also to reduce occupational hazard for the staff performing the identification, all specimens must be prepared carefully following the instructions below before submission to the IMR.
Generally all mites and ticks can be sent live or preserved in 70% alcohol. It is preferred that specimens be sent in 70% alcohol. If live specimens are sent, the container must be clearly labelled "HAZARDOUS – LIVE SPECIMENS". When sending live ticks, place the ticks inside a sealed container with a piece of damp filter paper inside to increase the humidity and prevent the specimen from dehydrating.
It is not advisable to send mounted mites unless the collector is experienced in mounting mites. Mounting of mites is a precise process and experience is required. If not done properly, it may damage the specimen making identification difficult or impossible. Although it is possible to remount specimens, some damage may occur during remounting. The IMR will undertake the mounting of the specimens.
SPECIMEN COLLECTION AND PREPARATION
Acarine specimens from humans
Sarcoptes scabiei (scabies mite)
The mite can usually be found in the stratum corneum of the following areas: the clefts between the fingers and toes, flexor surface of the wrist, extensor surface of the elbow, the axilla, penis, scrotum, and under the breast.
Skin scrapping is generally not suitable for the collection of scabies mites. The mites can be damaged by the procedure and the relatively large mass of skin cell debris makes it difficult to find the mites. Intact mites are necessary for accurate identification. If skin scrapings are submitted, the specimens must be sent in 70% alcohol. DO NOT SUBMIT THE SKIN SCRAPPINGS IN ITS NATURAL FORM as it may be hazardous to the person processing the specimen.
The recommended technique to collect scabies mites is to first locate the burrows made by the mites in the skin of the patients. Once located, a sharp sterile needle or lancet is used to slowly tease open the burrow until a small white object, which is the scabies mite, is observed. The mites can be picked up using the moistened sharpened end of a wooden application stick and placed in 70% alcohol.
Ticks in the ear canal
Ticks have been observed in the ear canal of patients and may cause facial paralysis unless removed. Ticks attached inside the ear canal can be removed by instilling warm water, mineral oil or 4% lignocaine. The solutions shall induce the ticks to detach; these ticks can then be removed using forceps.
Other ectoparasitic acari
This will require detailed examination of the affected part or whole body of the patient. A hand lens will assist in locating these acari. Use fine forceps to grip larger mites as near to the skin as possible and pull gently away. Smaller mites should be teased from the skin using a sharp sterile needle or lancet.
Other endoparasitic acari
These are usually found in dissected or autopsy tissues. The tissues are examined under a dissecting microscope and may need to be teased apart to expose any mites; the mites can be removed using needles and placed in 70% alcohol. The tissues may be put in 70% alcohol and send to the IMR if facilities and experience is not available for the removal of endoparasitic mites.
Acarine specimens from animals
Ectoparasitic acari
Live animal hosts must be anaesthetized before extraction of ectoparasites. The following process is to be used for small mammals such as rodents. Place each small animal in a cloth bag. Put the animal and cloth bag in a glass jar with a cotton wad soaked with chloroform. After 5 minutes, or longer for larger mammals, the cloth bag containing the animal is taken out off the glass jar. Ensure the animal is anaesthetized and then removed from the cloth bag. The cloth bag is turned inside out and shaken over a white enamel tray. The bag and tray is carefully examined for detached ectoparasites. Acari can be picked up using the moistened sharpened end of a wooden applicator stick and place in 70% alcohol.
The animal is next placed on a white enamel tray and brushed with a fine-tooth comb. This will dislodge most mites and ticks. Check for these acari in the enamel tray. Pick up any acari as above and place in 70% alcohol.
Animals should be examined for acari which are not dislodged by combing. Where possible, examine the animal under a dissecting microscope. Use a pointed forceps to remove any acari. Ticks should be gripped at the gnathosome (head) as close as possible to the skin of the host. Pull away gently from the skin. A sharp needle may be used to tease the skin around the attached ticks to assist in its removal. Care must be taken not to separate the head of the tick from the rest of the body. The tick must be intact for accurate identification. Place the acari in 70% alcohol.
Endoparasitic acari
Internal organs and tissue of animals suspected to contain endoparasitic acari should be removed and placed in 70% alcohol.
Acarine specimens from the environment
Ectoparasitic acari on vegetation
Many unfed ectoparasitic acari, especially ticks, climb onto surrounding vegetation such as tall grasses, leaves of small plants, shrubs, etc., to wait for a host to pass by. The vegetation and underside of leaves can be examined. Moisten the sharpened end of a wooden applicator stick or a fine brush, to pick up the acari and place in 70%.
A procedure known as 'flagging' is an effective way to collect acari especially ticks from vegetation. A white flannel cloth is tied to a stout stick and used to brush/sweep the vegetation. Ectoparasitic acari detach from the vegetation and attach to the moving cloth. The cloth is examined and any acari found can be removed using the above stated procedure.
Black Formica or plastic rectangular plates (usually 10 x 13 cm) can be placed beneath vegetation or inside ground burrows or holes to collect mites. After about 5 minutes, the plates are examined and any acari found can be removed using the above stated procedure.
Leaf litters, animal nests or soil suspected to harbour acari can be collected into plastic bags. A few pieces of damp filter paper or tissue paper are put in the bags to keep the contents moist. The bags are heat sealed and sent as soon as possible to the IMR.
Acari in houses
Occasionally acari can be seen inside houses. Moisten the sharpened end of an applicator stick or a fine brush, to pick up the acari and place in 70% alcohol.
Rodent and bird nests in houses (usually in the attic or roof) may harbour mites that can bite humans. These nests can be collected into plastic bags. A few pieces of damp filter paper or tissue paper are put in the bags to keep the contents moist. The bags are heat sealed and sent as soon as possible to the IMR.
Dust suspected to contain acari can be collected using a vacuum cleaner. Use a new vacuum bag for each sample. Place each vacuum bag in a plastic bag. Heat seal the plastic bag and send immediately to the IMR. Store the plastic bags in the lower compartment of a refrigerator if the bags could not be sent to the IMR on the day the specimen is collected.
