Further evidence of occurrence of Argas persicus Oken 1881 in free-range village chickens in Tanzania
E S Swai, E D Karimuribo* and P Kyakaisho**
Veterinary Investigation Centre, PO Box 1068, Arusha,
Tanzaniaemasw@yahoo.co.uk
*Department of Veterinary Medicine and Public Health,
Sokoine University of Agriculture, (SUA), Box 3021, Morogoro,
Tanzania
** District Veterinary Office, PO Box 20, Muheza,
Tanzania
Abstract
A survey to investigate and to identify soft tick like locally known as 'Paazi' in three villages of Muheza district, Tanzania was conducted during the period of June 2006. Different stages of ticks were collected from chicken, crevices in walls of chicken houses or in wooden materials such as windows or doors of buildings where the birds were sleeping for morphological identification using tick identification keys.
Laboratory investigation of the collected ticks revealed the 'Paazi' ticks to be soft ticks belonging to the genus Argas and species persicus. The observed Argas persicus in north east coast of Tanzania present another milestone in the record of this tick spp. Argas persicus has extended its range from its known presence in South Central Kenya to northern east coast of Tanzania possibly due to transportation of live birds through trade or as gift along the northern east coast border of Tanzania and Kenya. Our study survey advocate for more work to be done in order to establish the role of the ticks in transmission of important poultry pathogens including the zoonotic implication to humans.
Keywords: Argas persicus, Free-range chickens, soft ticks, Tanga, Tanzania
Introduction
Of the chickens kept in Tanzania, 75% are kept in rural areas under the traditional scavenging system (Melewas 1989). Rural chickens are characterized by low production coefficients (Minga et al 1999; Kitali 1998). A number of production constraints include animal health, housing and other management-related issues. Previous studies carried out in Tanzania reported the following animal health constraints: Newcastle Disease, fowl typhoid, helminth infestation, infectious coryza, chicken pox, poisoning, predators, ectoparasites mainly soft ticks and fleas (Minga et al 1999; Salum et al 2002).
Of the ectoparasites, argasid ticks spp. has been shown to contribute considerable loss to rural chicken (Okaeme 1988; Permin et al 2002). Information on the distribution and the role they played in village chicken in Tanzania is sparse and largely unknown. Walker et al 2003, along the east edge of Lake Victoria region, made the only recorded evidence of the existence of this tick spp. The objective of this study is to describe, confirm and for the first time to report the extension of this tick spp into some areas that where not initially thought of to harbour this soft tick species.
Material and methods
Study sites
Upon request from Muheza local government authority, scientists from local laboratory/investigation centre (VIC-Arusha and SUA-Morogoro) were invited to assess and investigate the problem of soft tick like (locally known as "Paazi") that was reported by poultry keepers to be a health and production constraint to rural scavenging chicken. Affected villages (Mahandakini, Gezani and Vunde Manyinyi) both located between Latitude 4 and 6 South of Equator and Longitude 36 and 38 East of Greenwich were visited during the period of June 2006 for detailed farmer interview and; tick collection and identification. The climate variables of the three villages represent typical tropical coastal; characterized by low altitude, wet, humid with two distinct rainy seasons namely: Long rains locally called 'masika' (occurring between March and May) and short rains locally called 'vuli' and occurring between September and October. These climate variables support many vectors of medical and veterinary importance including hard and soft ticks.
Tick collection, storage and identification
In order to identify the 'Paazi' soft ticks, efforts were made to collect different stages of ticks from local chicken (Plate 1) and also from the environment, which were mainly crevices in walls of chicken houses (Plate 2) or in wooden materials such as windows (Plate 3) or doors of buildings where the birds were sleeping. This exercise was facilitated by farmers themselves as they had enough experience in locating different areas on the chicken body and also in the environment where the 'Paazi' soft ticks were likely to be found. The ticks collected were placed in a container containing 70% alcohol before being transported to the Entomology laboratory at the Faculty of Veterinary Medicine, Sokoine University of Agriculture and the Veterinary Investigation Centre (VIC-Arusha) for further identification (Plate 4).
The ticks were identified using tick identification keys available from different sources (Ruedisueli and Manship 2006;Walker et al 2003; Bowman and Lynn 1995). Important morphological features used in tick identification included size of the tick, position of head and mouthparts (capitulum) relative to the thorax and abdomen on dorsal and ventral views and shape of the body. Laboratory investigation of the collected ticks revealed the 'Paazi' ticks to be soft ticks belonging to the genus Argas (Walker et al 2003). This was based on the presence of a ventral (sub-terminal) capitulum (Plate 5), absence of scutum or festoons and legs, which were unarmed (Ruedisueli and Manship 2006).
Plate 5: Dorsal view (left) and ventral view (right) of Argas persicus using stereo microscope
Results and discussion
Farmer responses suggested that the soft ticks have been in the area for the last 20 or 30 years. According to tick distribution map in Tanzania (Walker et al 2003), soft ticks (i.e. Argas persicus) were first reported in the Northern Tanzania (East of Lake Victoria and north east part of Mara region). In other part of East Africa, ticks are reported in South central of Kenya (near Voi or Tsavo wildlife area). The observed Argas persicus in north east coast of Tanzania present another milestone in the record of this tick spp. Argas persicus has extended its range from its known presence in South Central Kenya to northern east coast of Tanzania. There is no any other documented evidence of the existence of Argas persicus so far in Tanzania. Intensive tick survey conducted in Tanzania in 1999 did not report presence of Argas persicus in northeastern coast of the country (Lynen et al 1999). This could have been due to the limited information on health hazard imparted on the susceptible tick host species i.e. chicken and other poultry species. The tick appears to have been spread to its present range as a result of transportation of live birds to various villages along the northern border of Tanzania/Kenya for different reasons including trade or gifts. Because of limited resources and time, our study could not answer questions such as the role of the ticks in transmission of important poultry pathogens reported elsewhere (DaMassa and Adler 1979; Permin et al 2002; Poulsen et al 2000) which include Borrelia anserina (causing fowl spirochetosis) and Aegyptianella pullorum (causing aegyptianellosis), however, this work has shed light on possible existence of this tick in parts other than those currently documented and considered to habour the ticks in Tanzania. Consistent with this, the zoonotic implication of ticks could not be elucidated. This area might be of research interest in the near future.
Acknowledgements
The authors wish to acknowledge the cooperation of many farmers, Muheza district field staff and technical staff at SUA and VIC. This paper is published with the permission from the Director of veterinary services in Tanzania. This study was funded by EZCORE- animal health research support grant.
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