Tsutsugamushi disease in Khanh Hoa province
Tsutsugamushi disease, or Japanese river fever, scrub typhus is a dangerous disease caused by Orientia (formerly Rickettsia) tsutsugamushi, an obligate intracellular gram-negative bacterium and transmitted by some species of trombiculid mites (Trombiculidae), commonly appears in Asia-Pacific.
In Vietnam, Tsutsugamushi disease had been detected in Saigon since 1915 according to Goutron's description. The disease had occured in midland and mountainous areas (Lagrangae, 1923), for a long time it has temporarily cooled down, in recent years it has appeared sporadically in many areas. From 1998 to 2005,the Hospital 110 had treated 168 cases of scrub typhus; from 2001 to 2003, the Institute of Clinical Medicine and Tropical Diseases (Bach Mai, Hanoi City) had provided medical treatment for 166 scrub typhus cases from 24 provinces of the North and North Central Vietnam; from January 2008 to June 2009, 39 cases had been treated at the Hospital 87 Nha Trang. According to the statistics of the Provincial General Hospital of Khanh Hoa, the District Health Center of Ninh Hoa and the Hospital 87 Nha Trang, fromJanuary 2008 to March 2010 there were 342 cases of scrub typhus in Khanh Hoa province. In order to have the scientific grounds for the suggestion of scrub typhus control measures for the community, the IMPE Quy Nhon has conducted the investigation of this disease at Ninh Thuong Commune, Ninh Hoa District and Vinh Phuong Commune, Nha Trang City. The results showed that:
In Ninh Thuong, there has four species of trombiculid mites: Leptotrombidium (Leptotrombidium) deliense (accounting for high rate), Eutrombicula wichmanni, Gahrliepia (Walchia) chinensis (theses three species are capable of transmitting Tsutsugamushi disease) and Eutrombicula hirsti. The major vector of L.(L) deliense parasitized with high density on the collected rats; the trombiculid mites that are able to transmit the disease mainly parasitize on the rats.
In Vinh Phuong, the three species of trombiculid mites included Leptotrombidium (Leptotrombidium) deliense (making up a high proportion), Gahrliepia (Walchia) chinensis (these two species are capable of transmitting scrub typhus) and Gahrliepia (Walchia) Pacifica.
Situation of scrub typhus patients in Khanh Hoa province
The developments of scrub typhus in Khanh Hoa from 2008 to November 2010 is presented in Chart 1 (the data of patients were collected from the Provincial General Hospital, District Medical Center of Ninh Hoa, the Hospital 87 Nha Trang).
Chart 1: The developments of scrub typhus in Khanh Hoa province from 2008 to November 2010
- From 2008 to November 2010 there were 471 cases of scrub typhus in the whole country, of which 2 were from M' Drak (Dak Lak province) and the rest of 469 were from Khanh Hoa province, mainly concentrating in Ninh Hoa (55.01%), Nha Trang City (27.93%), Dien Khanh (7.46%), Cam Lam (3.62%), Van Ninh (2.99%), etc.
- In Khanh Hoa, Tsutsugamushi disease occurs all year round with the two peak periods of the disease transmission: June to July and November to December.
Number of patients
Nha Trang City
Cam Ranh City
Some epidemiological elements of Tsutsugamushi disease
At Ninh Thuong-Ninh Hoa
- Vector: the major vector of Tsutsugamushi disease L.(L) deliense has a high parasitic density on the rats collected in locality with 3.33 on a black rat and 2.50 on a house mouse. The two species capable of transmitting Tsutsugamushi disease are E. wichmanniand G.(W) chinensis.
- The patients' houses with rank gardens, near to ricefields: 7/11 * 100/100 = 63.64%.
- Patients with the habit of tilling the fields in forests: 2/11 * 100/100 = 18.18%.
- Patients aged 16 and older: 7/11 * 100/100 = 63.64%, children: 4 / 11 * 100/100 = 36.36%.
There was a low proportion of scrub typhus patients who often worked in the forests (18.18%) and a rather high rate of child ones (under the age of 16) who didn't come to the scrub typhus-endemic mountains (36.36%); this proved that in the areas of population and rice fields, the mites carried germs of scrub typhus.
Orchard habitat in Ninh Thuong, Ninh Hoa.
At Vinh Phuong, Nha Trang
- Vector: the major vector of Tsutsugamushi diseaseL.(L) delienseparasitized on the rats collected in the locality with the density of 1.33 on a black rat and 1.20 on a baby field-mouse; the vector that was likely to transmit the disease was G.(W) chinensis.
- Patients owning farmhouses, working or settling in areas close to the mountain pass of Ru Ri: 10/16 * 100/100 = 62.50%.
- Patients aged 16 and older: 16/16 * 100/100 = 100%, children: 0/16 * 100/100 = 0%.
There exists the major vector of Tsutsugamushi diseasein this area. There were a relatively high percentage (62.50%) of patients possessing farms, working or settling in areas close to the Ru Ri pass and a high rate (100%) of adult patients, which demonstrated that the area of Ru Ri Pass has the pathogen of scrub typhus.
The two surveyed sites are both likely to spread scrub typhus on the premises. The health facilities at grassroots level should make the recommendations to the people that while spraying chemicals to protect crops plants and livestock, they should spray the plants around, at the same time conduct bush clearance, regularly wear trousers and bind the trouser legs with elastic cord as working in the fields and farms, wash the working clothing after a working day, and impregnate the clothes with insecticides containing Pyrethroid, etc.
The habitat of scrub typhus in the area of Ru Ri Pass.
If the people in these two areas come to the communal medical station due to fever, the health staff should think of Tsutsugamushi disease beside other common feverous diseases.
Recommend the people to enhance the awareness of self-protection against Tsutsugamushi disease before the time of June to July and November to December annually.