A Ouadah, D Zahedi, R Perumal
animal behaviour, animal species, b.pseudomallei transmission, environment factor, epidemiology study, melioidosis frequency, public health importance
A Ouadah, D Zahedi, R Perumal. Animal Melioidosis Surveillance In Sabah. The Internet Journal of Veterinary Medicine. 2006 Volume 2 Number 2.
Melioidosis is an infectious disease of public health importance which it was first described in Malaysia in 1913 among laboratory guinea pigs and rabbits; though the disease was first reported in breeding stock of pigs imported from Australia in 1963 in Sabah. Infection occurs in different animal species, most frequently terrestrial and marine mammals both in domestic and wild animal with chronicity, silently and wide range of symptoms. The transmission of the pathogen B.pseudomallei and the fluctuation on melioidosis frequency during dry and wet seasons are strongly gathered and supported by environmental factors such as temperature, rainfall and different soil type's compositions.
Melioidosis is a zoonotic infection of public health importance. It is described most often in domestic animals and humans in Southeast Asia and other parts of the world (Puthucheary et al, 2001; Jones et al, 1996). It is an emerging infectious disease with serious public health implications in most countries (Center for Food Security and Public Health, 2003). Transmission occurred when infected animal body fluids such as urine, milk or nasal secretion or blood came into direct contact with susceptible hosts depending on the site of infection or through contact with infected soil or water (Center for Food Security and Public Health, 2003; Jayaram, 2000; Bettey et al, 2002; May-Ann et al, 2000); as well infection appears to be the inhalation and aspiration of contaminated dust particles (Weber et al, 1969; Mackowiak et al, 1978; Thomas et al, 1988; Howe et al, 1971). Moreover, infection has been reported through contact with contaminated domestic and medical appliances (Mccormick et al, 1975; Schlech et al, 1981), and trans-placental (Thomas et al, 1988; Jodie et al, 2000), nosocomial (Jodie et al, 2000; Sookpranee et al, 1989) or sexual (Currie, 2000b) has been also reported. The incubation period of melioidosis is not clearly defined but may range to one to 21 days (Ian, 2002; Leelarasamee, 2000).
In Malaysia, melioidosis was mostly common discovered in variety livestock such as goats, cattle and pigs. The earlier case was reported in Kuala Lumpur, a cat in 1918, where it was died after illness of three days suffering with dysentery, vomiting and prostration. Melioidosis in Sabah was first reported in breeding stock of pigs imported from Australia in 1963 in Keningau (Sabah, 1963). Subsequently in 1965,
Common symptoms of melioidosis in animal were anorexia, pyrexia, hyperthermia and cough; skin dehydratations were often seen. During the early infection, disease progress silently for a considerable period and often resulted in death but symptoms and disease progression is different from species. Goat melioidosis runs more chronic, silent progression with unusual progressive emaciation and inanition (Vellayan, 1994). Both acute and chronic forms occur in sheep are very similar to those in goats, whereas some show nervous signs; paraplegia. Melioidosis in equidae is rare where
Animal Disease Research Centre (ADRC) in Kota Kinabalu, Sabah records showed the most common disease was pasteurelosis followed by melioidosis during the period between 1994 and 2003. Through the data on animal melioidosis were obtained from ADRC records for the period 1994 to 2003 showed three hundred forty one (341) melioidosis cases were identified from 12139 at post-mortem (Table 1). The post mortem examination revealed lesions in liver, spleen, kidney, cardiac and respiratory systems, skin, muscle, and lymph nodes. Liver, spleen, tracheal and bronchial tubes were congested often with multiple abscesses; also focal subcutaneous and muscle haemorrhages and dilatation of the heart seen. In fact, ante mortem studies showed different symptoms between animal species, even the symptoms are varied in different species of Zoo animals (Vellayan, 1994).Common symptoms seen were anorexia, pyrexia, hyperthermia and cough; skin dehydratations were often seen; on the other hand, various ages of animals were infected but the disease is more acute and fatal for young animals. The ratio of 7: 5 between males and females, it seems that females were most frequently infected than males.
Table 1 showed that the disease affected most frequently animals living forest or according to their active behaviour such as monkey (11.11%), orangutan (8.92%), goat (8.01%) and deer (5.19%) and less often for captive animal; big ruminant and non-ruminant such cattle (0.23%), buffalo (0.39%), horse (0.63%), pig (0.72%), as well as wild bird (0.22%).
Veterinary records showed as well that large ruminant such as cattle and buffalo were rarely seen infected with melioidosis. Perhaps, the inactive behaviours of these animals on pasture lessen the contact with the disease agents. Also, the animal may have develop some tolerance or resistance to the bacteria, e.g buffaloes are semi-aquatic spending a large part of their time either in water or swamp wallows, thus protecting skin injuries or abrasion from infections. Dogs and cuts were rarely reported with melioidosis; though in ADRC had one cases in cat (1.63%). It is believe that is an unusual case. ADRC had reported no melioidosis cases for domestic birds during past ten years in Sabah. It was suggested though not yet proven that domestic chickens are resistant to melioidosis (Stanton and Fletcher, 1932; Lim et al, 1967).
High temperature and low raining at dry season graphs showed these two parameters run approximately opposite and low disease incidence through that period (Figure 2); only on 1995 and 1996 had moderate melioidosis frequencies.
However, graph of low temperature and important rainfall in figure 3 runs almost on parallel from 1994 to 1999, and during that's period highest melioidosis frequency with maximum peak in 1995 rather than the next period from 2000 to 2000 which the two environmental parameter run on opposite as consequences to low melioidosis frequency.
The analyzed data shown that during the dry season December till May, there were weak negative correlations both for temperature and rainfall respectively (y = -2.1199x + 94.756; R 2 = 0.0011; r = -0.03), (y = 0.0082x + 38.407; R 2 = 0.0004; r = -0.02) and melioidosis. Otherwise, the analysed data shown that during the wet season June till November, the disease had weak positive correlation with temperature (y = -0.0082x + 38.407; R 2 = 0.0004; r = -0.02) and moderate positive correlation with rainfall (y = 0.3783x – 41.55; R 2 = 0.2347; r = +0.48).
Middling melioidosis is an infectious disease of public health importance, and infect most often terrestrial and aquatic mammals, especially in Southeast Asia and other parts of the world. Malaysia is a tropical country rich on biological diversity; which the environmental factors encourage high levels of biodiversity in hosts, factors,
It is obvious that there was decrease in melioidosis cases in animal with increase in environmental temperature, in reality; it is seems that dry environment does not encourage transmission of the disease among animal. Conversely, it is suggested that that wet environment predisposes animal to a higher exposure of getting infection, possibly from contaminated soil.
We thank Mr. Awang Sahak Salleh and Dr. Nasip Eli from Department of Veterinary Services and Animal Industry, and Animal Disease Research Centre in Kota Kinabalu, Sabah for providing the data required for this study. Also we thank Jabatn Hidrologi dan Perkhidmatan Kajicuaca Malaysia.