• Users Online: 202
  • Home
  • Print this page
  • Email this page
Home About us Editorial board Ahead of print Current issue Search Archives Submit article Instructions Subscribe Contacts Login 


 
 
Table of Contents
RESEARCH ARTICLE
Year : 2021  |  Volume : 58  |  Issue : 2  |  Page : 141-147

A comparative study to evaluate wonder and Sherman traps for the surveillance of ectoparasitic chigger vector mites of the scrub typhus


ICMR-Vector Control Research Centre, Field Station, Madurai, Department of Health Research, No.4, Sarojini Street, Chinnachokkikulam, Tamil Nadu, India

Date of Submission09-Sep-2019
Date of Acceptance17-Feb-2020
Date of Web Publication13-Jan-2022

Correspondence Address:
Philip Samuel Paulraj
ICMR-Vector Control Research Centre, Field Station, Madurai, Department of Health Research, No.4, Sarojini Street, Chinnachokkikulam, Madurai-625002, Tamil Nadu
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0972-9062.321752

Rights and Permissions
  Abstract 

Background & objectives: Scrub typhus is caused by Orientia tsutsugamushi and transmitted by larval trombiculid chigger mites. Rodents and shrews are hosts for chigger mites in the transmission to humans. Wonder and Sherman traps are widely used for trapping rodents and shrews for the collection of ectoparasitic chigger mites. A comparative trapping study was undertaken in different villages in Vellore district, Tamil Nadu and Thiruvananthapuram district, Kerala, India to evaluate the efficiency of traps for trapping rodents & shrews.
Methods: Wonder and Sherman traps were set in outdoors and indoors to capture the rodents. Wonder Traps, large wired cage, and Sherman Traps are foldable. These traps were employed for the rodents/ shrew surveillance to gather chigger vector mites. Identification of rodents, chigger mites and Trap index were observed.
Results: Z Test comparing the capture rates showed wonder trap (P<0.001) to be significantly more efficient than the Sherman traps. The number of rodents /shrews collected in a Sherman trap was always one. But the number of rodents /shrews collected in a positive wonder tap was 2.83 in both states, 2.25 and 1.24 in Tamil Nadu and Kerala, respectively. Wonder traps (77%) were found more attractive in collecting more rodents in Tamil Nadu compared to Sherman traps (23%). But the Sherman trap (60.9%) was found efficient in collecting more shrews in Kerala compared to wonder traps (39.1%). Shrew’s collection was more in Sherman collections from both Tamil Nadu and Kerala. In Tamil Nadu and Kerala sex-wise collection of Male & female rodent/shrew was uniformly found in both the wonder (85% &75%) and Sherman traps (86% & 83%) with a maximum proportion of females.
Interpretation & conclusion: Sherman traps can be used as single-capture live traps and on the other hand wonder traps can be used as multiple-capture live-traps. The geographical distribution pattern of various rodents trapped can be determined to identify the target areas for control of a particular species and also for the control of selected species. Mostly females were captured abundantly in both wonder and Sherman traps. In wonder traps, female rodents were trapped as family members in large numbers. Wonder traps are more attractive for trapping more rodents. This study addressed the careful choice of wonder traps for ectoparasitic chigger vector surveillance.

Keywords: Ectoparasites; Rodents/ Shrews; Scrub Typhus; Sherman; Wonder Traps


How to cite this article:
Paulraj PS, Renu G, Ranganathan K, Veeramanoharan R. A comparative study to evaluate wonder and Sherman traps for the surveillance of ectoparasitic chigger vector mites of the scrub typhus. J Vector Borne Dis 2021;58:141-7

How to cite this URL:
Paulraj PS, Renu G, Ranganathan K, Veeramanoharan R. A comparative study to evaluate wonder and Sherman traps for the surveillance of ectoparasitic chigger vector mites of the scrub typhus. J Vector Borne Dis [serial online] 2021 [cited 2022 Jan 26];58:141-7. Available from: https://www.jvbd.org/text.asp?2021/58/2/141/321752


  Introduction Top


Vector-borne diseases have been known to mankind since ancient times[1]. One such vector-borne disease which has re-emerged in India in the 21st century is scrub typhus. Scrub typhus, known as tsutsugamushi disease is a medically significant rodent-borne zoonotic disease transmitted by small animals such as rodents and shrews and to humans by some species of larval trombiculid chigger mites. The causative agent of scrub typhus is the gram-negative obligate intracellular bacterium Orientia tsutsugamushi. Mites carry the bacterium from larval stages to adults and their progenies through transstadial and transovarial transmission. Approximately one million cases of scrub typhus occur each year and more than a billion people are at risk worldwide[2]. Scrub typhus infection can cause severe multi-organ failure with a case fatality rate of up to 70% without appropriate treatment[3]. When a study was undertaken to examine the abundance and distribution of trombiculid mite vectors from scrub typhus endemic Vellore district Tamil Nadu and Thiruvananthapuram district Kerala in India - a comparison of trapping efficacy of the two different traps wonder and Sherman traps used to trap rodents/shrews were evaluated.

Different rodent traps were used to capture the small mammals like rodents/shrews and randomly sampled using live traps for monitoring their population size[3],[4] and to survey the chigger mites, ticks and fleas present on them to understand the rodent-borne diseases in detail[2],[4],[5],[6],[7]. Sherman and wonder traps were used for the live rodent trapping in many places to study in detail the scrub typhus vector chigger mites[6]. At the same time in many other similar studies, Sherman traps[2] were exclusively used for the collection of all rodents and shrews. A recent study conducted in Puducherry, India used Sherman traps alone for the surveillance[2]. On many occasions, different types of traps such as cage-type live trap, box type live trap, wooden live trap, tin made snap trap and wooden were used for rodent collection[8]. One type of trap caught more animals, more species, different size (age), classes or more of one sex than the other[10]. Even though many traps were used for the rodent trapping, a systematic longitudinal comparative study like this was so far not undertaken anywhere and reported. The study was undertaken to examine the abundance and distribution of trombiculid mite vectors from scrub typhus endemic Vellore district Tamil Nadu and Thiruvananthapuram district Kerala of India. Two types of traps wonder and Sherman traps were used to trap rodents/shrews. The present study conducted to capture live rodents/shrews using Sherman and wonder traps were thus compared to show their relative efficiency to collect more rodents/shrews used for the routine surveillance of the scrub typhus chigger vector mites. These traps were employed to make it worthy for the rodents/ shrew surveillance to gather chigger vector mites to understand the scrub typhus transmission in the endemic areas of Tamil Nadu and Kerala. Thus it was decided to bring out the best trap which can fetch a number of live animals to be used judiciously for our field studies.


  Material & Methods Top


Study sites

The study sites were the Vellore district of Tamil Nadu and Thiruvananthapuram district of Kerala, India. These districts were selected based on the outbreak of scrub typhus. Vellore district, from Tamil Nadu, covers an area of 6,077 sq. km with a semi-arid climate, lies in the Eastern Ghats region and Palar river basin, almost plain with slopes from west to east, located between 12-15°N 78-20°E and 13-15°N 79-50°E. Trivandrum district, from Kerala, covers an area of 2,192 km2 located between 8.17°N 76.41°E and 8.54°N 77.17°E, divided into three geographical regions as Western Ghats Highlands, Plateau Midlands with tiny hills and valleys, and Coastal Lowlands comparatively narrow, consisting of rivers, deltas, and seashore.

During 2014–2016, 1746 scrub typhus cases were confirmed in Thiruvananthapuram district Kerala with the largest outbreak occurred in 2015 with 947 (54.23%) cases. The reminder 442 cases were reported in 2016. Similarly, Vellore district of Tamil Nadu reported 468 confirmed scrub typhus cases from 2013–2016 with maximum cases reported in 2013 (167 cases) (35.68%) followed by 140 cases in 2016 (29.6%).

Study areas were selected based on online listing of scrub typhus cases reported both in Tamil Nadu and Kerala. The Primary Health Centers (PHCs) recorded maximum scrub typhus cases and they were selected and longitudinal studies were undertaken in those areas. These areas included the Vellore district in Tamil Nadu and Thiruvananthapuram district in Kerala. Thus from Vellore district, Tamil Nadu Munjurpet, Kanyambadi CHC, Ponai PHC, Anaicut PHC, Agravaram, Lalapet PHC and Sathyamangalam, Poigai PHC areas were selected. In Thiruvananthapuram district five areas viz. Pazhamoodu, Karakulam PHC, Pangayil, Aruvikara PHC, Pavachakuzhi, Vilavoorkal PHC, Kidarakuzhi, Vizhinjam PHC and Kollamthara, Thiruvallam PHC were selected.

Trap description

These two types of universally used traps, wonder and Sherman traps were set outdoors (peri-domestic areas) and indoors (domestic areas) for the capture of rodents. The Sherman trap is a box-style animal single capture trap designed for the live capture of small mammals such as mice, voles, shrews, and chipmunks. The Sherman trap is foldable, Aluminum metallic, weightless and easy to handle in fields measuring the size of 3” × 3” × 10” (W × H × L), designed for live capture of rats consisting of eight hinged pieces of aluminum sheet metal that allow the trap to be collapsed for storage or transport[2],[9]. Sherman traps are often set in grids and maybe baited with grains and seed. The hinged design allows the trap to fold up flat into something only the width of one side panel. This makes it compact for storage and easy to transport to field locations. Both ends are hinged, but in normal operation, the rear end is closed and the front folds inwards and latches the treadle, trigger plate, in place. When an animal enters far enough to be clear of the front door, their weight releases the latch and the door closes behind them. The lure or bait is placed at the far end and can be dropped in place through the rear-hinged door[11] [Figure 1]. Wonder traps are larger; iron wired with the hook, easy to carry in the field and can capture more rodents at a time (8 to 10 Nos.) [Figure 2]. Wonder traps multiple capture traps found well in the efficacy of trapping for single and multiple species of rodents. Wonder traps are also weightless and metallic wired, large in the size, the trapped rodents are visible by the wired surfaces (60 cm x 22.5 cm).
Figure 1: Sherman Trap

Click here to view
Figure 2: Wonder Trap

Click here to view


Rodent trappings

Rodent trappings were undertaken to determine the prevalence of rodent species, vector mites, and the chigger infestation rate. Sherman/wonder traps were set up near the rodent burrows showing evidence of the rodent activity. In each of the scrub typhus positive selected village, 50 traps were set outdoors (peri-domestic areas) with scrubby vegetation and rodent burrows. Traps were set in the evening (6.00 pm) and the traps were retrieved the next day morning (7.00 am). The captured animals’ rodents/ shrews were anesthetized and identified through morphological features[12],[13],[14],[15],[16].

Ectoparasites collection

The ectoparasites especially chigger (larval) mites were collected by combing the animals against the fur over a white enamel tray. The snout, ears, limbs and axillary regions of individual animals were combed[2]. Chigger collections could be made from the rat ear pinna region and highly infested shrew’s hind leg region. The chiggers collected from these animals were preserved in 70% ethanol until they were mounted on slides. Mites were mounted in Hoyer’s medium[17], examined under the microscope and identified up to species level, following standard taxonomical keys. Other ectoparasites collected were mounted in Hoyer’s medium, examined under the microscope and identified using the standard taxonomical keys[18],[19],[20]. Longitudinal studies were undertaken in these two different localities of the states Tamil Nadu and Kerala in the alternate months from September 2017 to August 2018.

Statistical analysis

The Abundance is a measure of the number of individuals captured adjusted by the number of traps deployed[21]. Efficiency between trap was measured using the Z Test.

Ethical statement

Animal Ethical Committee clearance was obtained for this study from the Institutional Animal Ethics Committee (IAEC) of Madurai Medical College; Madurai, India.


  Results Top


At the various study sites of Vellore, Tamil Nadu, a total of 860 Sherman traps and 590 Wonder traps were placed for trapping rodents and shrews. In Thiruvananthapuram, Kerala, 842 Sherman traps and 600 Wonder traps were placed for trapping rodents and shrews.

Tamil Nadu

Out of 860 Sherman traps laid at the Vellore district of Tamil Nadu, only 72 traps were found positive (8.37%) with 72 rats or shrews and the number of rodents/shrew collected per trap was 1.0. Single rodent per trap was captured in the Sherman traps. A total of 10 male (13.89%) and 62 female rats/shrews (86.11%) were captured comprising different species like Mus musculus 4 female (5.6 %), Rattus norvegicus 1 female (1.4%), Rattus rattus 3 male and 31 female (47.2 %) and Suncus murinus 7 male and 26 female (45.8 %). Thus a total of six different species of rodents/shrews Mus musculus, Rattus norvegicus, Rattus rattus, Suncus murinus, Bandicota bengalensis and Tatera indica were collected in wonder traps whereas in Sherman trap only four species of rodents/shrews Mus musculus, Rattus norvegicus, Rattu srattus and Suncus murinus were collected.

Likewise, out of 590 Wonder traps placed 106 traps (17.97%) were found positive with 241 rats or shrews at the various study sites of Vellore district of Tamil Nadu. Out of the 106 positive wonder traps obtained, only 52 positive wonder traps had single rats or shrews captured and the number collected per trap was 1.0. Similarly, the rest of the total 106 positive wonder traps were obtained, 54 traps showed 189 rats/shrews trapped a group of mixed species with both sexes and the total collection in wonder traps in Tamil Nadu was 2.274 with the number of rats or shrews trapped ranging from 2–11 of rats/shrews per trap. A total of 36 male (14.9%) and 205 female (85.1%) rats/ shrews were captured comprising of different species Mus musculus 23 female (9.5%), Rattus norvegicus 4 male and 3 female (2.9%), Rattus rattus 30 male and 170 female (83 %), Suncus murinus 1 male and 3 female (1.7 %), Bandicota bengalensis 1 male and 4 female (2.1 %) and Tatera indica 2 female (0.8 %) [Table 1] and [Figure 3].
Figure 3: Total Number of rodents and shrews trapped by wonder and Sherman traps in Tamil Nadu and Kerala

Click here to view
Table 1: Percentage composition of the trapped rodents in different traps kept in Tamil Nadu and Kerala

Click here to view


Kerala

Similarly, a study conducted in Thiruvananthapuram district of Kerala showed, out of 842 Sherman traps laid, only 95 traps were found positive (11.28%) and the number of rodent per trap was 1.0. A total of 16 male (16.8%) and 79 female (83.2%) rats/shrews were captured comprising of different species Mus musculus 2 male and 9 female (5.6 %), Rattus norvegicus 3 female (3.2%), Rattus rattus 13 female (13.7 %), Suncus murinus 13 male and 51 female (67.4 %) and Bandicota bengalensis 1 male and 3 female (4.2 %).

Likewise, out of 600 Wonder traps placed 50 traps were found positive for rats or shrews (8.3%) at the various study sites of Thiruvananthapuram district of Kerala. Out of the 50 positive wonder trap positives obtained, only 42 positive wonder traps had single rats or shrews captured and the number per trap was 1.0. Similarly, the rest of the 8 positive wonder trap positives obtained 19 rats/shrews and the total collection in wonder traps in Kerala was 1.22 [Table 2] with the number ranging from 2-5 of rats/shrews per trap. A total of 20 male (32.8%) and 41 female (67.2%) rats/shrews were captured comprising of different species Mus musculus 1 female (1.6 %), Rattus norvegicus 4 female (6.6%), Rattus rattus 10 male and 24 female (55.7 %), Suncus murinus 6 male and 1 female (11.5 %) and Bandicota bengalensis 4 male and 11 female (24.5 %) [Table 1] and [Figure 3].
Table 2: Details of the mites per animal collected in the different traps

Click here to view


Thus, a total of 5 different species of rodents/shrews Mus musculus, Rattus norvegicus, Rattus rattus, Suncus murinus, and Bandicota bengalensis were collected in both wonder and Sherman traps. Only Suncus murinus and the young ones of Bandicota bengalensis species of rodents were collected more in Sherman traps placed in Kerala. Total collection particulars and the percentage composition of different species of rodents/shrews are mentioned in [Table 1] and [Figure 3]. Rattus rattus was collected more in the Wonder traps both in Tamil Nadu (84%) and Kerala (55.7%).

The ratio of different rodents/shrews collected in wonder and Sherman traps showed more shrews collection in Sherman traps from both Tamil Nadu and Kerala (1:8.25 & 1:9) [Table 3]. But the number of mites per animal collection in the different traps showed more mites collection from the Suncus murinus from both Tamil Nadu (443 mites/ animal) and Kerala (49.5 mites/animal) by wonder traps [Table 2].
Table 3: The ratio of collection of rodents /shrews from different traps

Click here to view


Total number of rodents/shrews trapped at wonder and Sherman traps in Tamil Nadu and Kerala in different period of time is shown in [Figure 4]. Total traps used for the collection of rodents/shrews were adjusted to calculate the total capture for 100 traps and compared. Wonder trap collection per 100 traps is 25.46 and Sherman trap collection per 100 traps is 9.811. Z Test comparing the capture rates showed wonder trap (P<0.001) to be significantly more efficient than the Sherman traps. This abundance index is a percentage measure of the number of individuals captured adjusted by the number of traps deployed.
Figure 4: Total number of Rodents/Shrews trapped at Wonder and Sherman traps - seasonally

Click here to view



  Discussion Top


Scrub typhus is a zoonotic disease, caused by Orientia tsutsugamushi, an obligate intracellular bacterium (Family: Rickettsiacceae) transmitted to humans by the bite of a larval Leptotrombidium mite Chiggers, particularly Leptotrombidium delienses found in areas of heavy scrub vegetation. Humans are accidental hosts in this zoonotic disease with a case fatality rate up to 70% without appropriate treatment[22]. Live trapping has been considered as the key technique for monitoring small mammal populations[23]. A study was undertaken to map the occurrence of the Trombiculid vectors in Tamil Nadu and Kerala and to demonstrate the circulation of the causative agent O. tsutsugamushi. For the rodent survey to monitor the abundance of scrub typhus chigger mites, two traps wonder and Sherman are widely used. Sherman traps yielded more species[6] than mesh[5] and pitfall[3] traps. These traps were considered to be efficient for catching shrews, but do not seem to be as effective for trapping mice[24].

Number of rodent/shrew collected in a wonder trap used for the longitudinal studies showed 2.83 in both the states followed by 2.25 in Tamil Nadu and 1.24 in Kerala which showed that wonder traps can collect more rodent/ shrew than the Sherman trap which always collected one as observed in the collections undertaken in Tamil Nadu and Kerala.

Even though on many occasions a single rat/shrew was collected in the wonder traps, wonder traps are spacious, well designed in such a way to accommodate more than one rodent/shrew at a time. Wonder traps were considered as an effective multi-catch trap[25]. Thus the wonder traps trapped more than one rodent/shrew on many occasions. Sherman traps always captured only one rodent or shrew but more than one rodent and shrew were trapped at a time in the Wonder traps which can be termed as the multiple captures live traps. Particularly the rodent species Rattus rattus was collected more in the Wonder traps both in Tamil Nadu (84%) and Kerala (55.7%). Thus the wonder traps which capture more than one animal on many occasions considered superior to that of Sherman traps.

Wonder traps are easily available in the market and cheaper than the Sherman traps. Sherman traps are not easily locally available and have to be imported or to be obtained from the local manufacturers at a higher price. Imported Sherman traps are costlier than the locally available wonder traps. Wonder traps yielded more species of rodents/shrews[6] than Sherman traps[4].

Whenever there is more than one individual trapped in a wonder trap, females were found with their young ones trapped easily as a family. All offspring were found following their mothers and they are trapped very easily at wonder traps as a group. More female rats were trapped both in Tamil Nadu and Kerala inside the wonder traps which are due to voracious feed searching behavior of females than males thus got easily trapped. Besides this, this study found out that the wonder traps can be utilized for the specific collection of Roof rats Rattus rattus, and also can be employed for trapping fast-moving rats. Based on this survey Rattus rattus was more common both in Tamil Nadu and Kerala. A single collection of Rattus rattus species numbering 10-15 collected without any ectoparasites and the size dimensions revealed that a family of rodents was collected.

Wonder traps found to attract more species of the mixed genus of rodents and rodents of different sex. Thus Wonder traps were found more efficient in trapping more species of rodents in domestic areas. By trapping single species ranging from 10–15 and collecting more than one species at one catch, wonder traps can be used for the biodiversity studies of the rodents in an area and thus used to find out the rodent species found distributed in an area.

Sherman trap, a single catch trap for rodents, was reported to be superior over snap traps. Museum special kill traps captured significantly more individuals of both western harvester mouse and house mouse than Sherman live traps in Missouri[9]. In this study, Sherman traps were found more efficient in trapping slow-moving Shrews in Kerala (95 nos.). Besides that, for trapping slow ground moving shrews, Suncus murinus, and also for small or baby bandicoots, Sherman traps worked well since the entry point of the Sherman trap is at ground level. Thus in Kerala, shrews Suncus murinus were trapped abundantly which indicated their abundant availability in the preferential ecological niches in Kerala. Sherman traps can easily be placed on the ground surface and will allow easy entry of the shrews. But in the case of wonder traps, a rodent has to slightly climb up to search the entry point of the trap which is difficult for the shrews. Wonder traps are larger and caught more species and larger rodents like Bandicota bengalensis in Tamil Nadu than the Sherman trap which collected young ones of Bandicota bengalensis and Suncus murinus in Kerala. Shrews are nocturnal creatures and mainly underground scavengers. Suncus murinus emerged as the most preferred host for the vector mites with a high proportion of chiggers collected from them. Shrews spend the day in a burrow or hiding place nearby human habitations. These surveys were mainly undertaken nearby human residential areas[2],[6].

In this study, a single wonder trap captured one type of rats belonging to a single Genus Rattus rattus ranging from 10-15 nos. Sometimes 2 species like Rattus rattus and Rattus norvegicus were collected in a single wonder trap. In addition to this, sometimes rats were captured belonging to 2 different genera like Bandicota sp. and Rattus sp. or Mus sp. and Rattus sp. Similarly, in a few occasions rats/shrew belonged to 3 different genera Mus sp, Rattus sp. &Tatera sp, and Mus sp, Rattus sp. and Suncus sp. were also jointly collected. By these collections, the geographical distribution pattern of various rodents can be determined to identify the target areas for control of a particular species and also for the control of selected species of female rodents found in large numbers using wonder traps that can be efficiently used. Mostly females were captured abundantly in both the wonder and Sherman traps.

The present study examined the trapping performance of both wonder and Sherman traps from the scrub typhus endemic areas during our ectoparasites collection on rodents/shrews. Z Test comparison showed wonder trap to be significantly more efficient than the Sherman traps. The requirement for a successful live-capture trap for common rats should be relatively large allowing several rats/ shrews at once[26]. Only wonder traps can catch more than one animal at a setting- multi-capture trap and considered as potentially more efficient traps than the single capture Sherman traps. A wonder trap door will not close preventing multiple animal entries and thus the entry door will not close after one animal entered the trap as observed in the Sherman trap. Thus one entry will not debar other animals’ entry and induce a higher level of trap shyness[26]. Based on the results obtained wonder traps captured more than one individual rats/shrews and specifically designed to allow captures of multiple species of rodents belonging to different genera and different species and thus wonder traps can efficiently be utilized for the routine surveillance of the rodents /shrews in the scrub typhus affected areas.

Conflict of interest: None



 
  References Top

1.
Quintal D. Historical aspects of the rickettsioses. Clin Dermatol 1996; 14: 237–242.  Back to cited text no. 1
    
2.
Sadanandane C, Ayyanar E, Paily K, Karthikeyan PA, Sundararajan A, Purushothama J. Abundance & distribution of trombiculid mites & Orientia tsutsugamushi, the vectors & pathogen of scrub typhus in rodents & shrews collected from Puducherry & Tamil Nadu, India. Indian J Med Res 2016; 144: 893–900.  Back to cited text no. 2
    
3.
Torre I, David Guixe, Fermi Sort. Comparing three live trapping methods for small mammal sampling in cultivated areas of Ne Spain. Hystrix It. J. Mamm. (n.s.) 2010; 21:147–155  Back to cited text no. 3
    
4.
Motro Y, Ghendler Y, Muller Y, Goldin Y, Chagina O, Rimon A, Harel Y & Motro U. A comparison of trapping efficacy of 11 rodent traps in agriculture Mammal Research 2019; https:// doi.org/10.1007/s13364-019-00424-7. (Accessed on January 1, 2019)  Back to cited text no. 4
    
5.
Han-Iiree, Woo-Hyun Chang, Sunho Kee, In-Yong Leei and Soung-HooJEoN. Detection of Orientia tsutsugamushi DNA in the individual using polymerase chain reaction in Korea trombiculids. Med Entomol Zool 1997; 48: 197–209.  Back to cited text no. 5
    
6.
Tilak R, Kunwar R, Wankhade UB, Tilak VW. The emergence of Schoengastiella ligula as the vector of a scrub typhus outbreak in Darjeeling: Has Leptotrombidium deliense been replaced? Indian J Public Health 2011; 55: 92–99.  Back to cited text no. 6
    
7.
Zhan YZ, Guo XG, Speakman JR, Zuo XH, Wu D, Wang QH, Yang ZH. Abundances and host relationships of chigger mites in Yunnan Province, China. Med Vet Entomol 2013; 27: 194–202.  Back to cited text no. 7
    
8.
Chaisiri K, Cosson JF, Morand S. Infection of Rodents by Orientia tsutsugamushi, the Agent of Scrub Typhus, in Relation to Land Use in Thailand. Trop Med Infect Dis 2017; 2: 53.  Back to cited text no. 8
    
9.
Eulinger KG, Burt MS Comparison of captures between Sherman live traps and Museum Special kill traps. Southwest Nat 2011; 56: 241–246.  Back to cited text no. 9
    
10.
Innes DGL and Bendell JF. A sampling of small mammals by different types of traps in Northern Ontario, Canada. Acta Theriologica 1988; 33: 443–450.  Back to cited text no. 10
    
11.
Anthony NM, Ribic CA, Bautz R and Garland T Jr. Comparative effectiveness of Longworth and Sherman live traps. Wildlife Society Bulletin 2005; 33:1018–1076.  Back to cited text no. 11
    
12.
Aplin KP, Brown PR, Jacob J, Krebs CJ and Singleton GR. Field methods for rodent studies in Asia and the Indo-Pacific. Canberra, Australia: Australian Centre for International Agricultural Research, Monograph 2003; 100: 1–223.  Back to cited text no. 12
    
13.
Cheruvat, Dinesan; Radhakrishnan, C. and Muhamed Jafer- Palot. 2006. Handbook on Mammals of Kerala. Zoological Survey of India 2006:1–154.  Back to cited text no. 13
    
14.
Aplin, K.P., Brown, P.R., Jacob, J., Krebs, C.J. and Singleton, G.R. Field methods for rodent studies in Asia and the Indo-Pacific. ACIAR Monograph 2003; 100:1–223.  Back to cited text no. 14
    
15.
Gratz NG. Rodents as carriers of diseases,. In: Buckle AP, Smith RH (eds) Rodent pests and their control. CAB International, Wallingford, UK 1994; 85–108.  Back to cited text no. 15
    
16.
Cunningham DM, Moors PJ (1996) Guide to the identification and collection of New Zealand, Wellington, New Zealand: Department of Conservation 1996; 3rd Ed., 1–24.  Back to cited text no. 16
    
17.
Krantz GW, Walter DEE (). A manual of Acarology, Texas Tech University Press, Texas, 3rd Edition 2009; 1–816.  Back to cited text no. 17
    
18.
Stan Fernandes SJ, Kulkarni SM. Studies on the Trombiculid Mite Fauna of India, Zoo. Surv. India, Kolkata Occ. Paper 2003; 212: 1–539.  Back to cited text no. 18
    
19.
Nadchatram M, Alexander L Dohany A pictorial key to the subfamilies, genera, and subgenera of Southeast Asian chiggers (Acari, Prostigmata, Trombiculidae). Bulletin / Institute for Medical Research, Malaysia 1974; 16.  Back to cited text no. 19
    
20.
Goff ML, Loomis RB, Welbourn WC, Wrenn WJ. A glossary of chigger terminology (Acari: Trombiculidae). J Med Entomol 1982; 19: 221–238.  Back to cited text no. 20
    
21.
Pacific Invasives Initiative Resource Kit for Rodent and Cat Eradication. Guidelines on Rodent Surveillance Techniques Version 1.0.3 2011; 1–36 www.pacificinvasivesinitiative.org/ rk/index.html. (Accessed on January 1, 2019)  Back to cited text no. 21
    
22.
Xu G, Walker DH, Jupiter D, Melby PC, Arcari CM. A review of the global epidemiology of scrub typhus. PLoSNegl Trop Dis 2017; 11: e0006062.  Back to cited text no. 22
    
23.
Flowerdew JR, Shore RF, Poulton SMC and Sparks TH. Live trapping to monitor small mammals in Britain. Mammal Rev 2004; 34: 31–50.  Back to cited text no. 23
    
24.
Andrzejewski R, Rajska E. Trappability of bank voles in pitfalls and live traps. Acta Theriol 1972; 17: 41–56.  Back to cited text no. 24
    
25.
Jain AP, Mathur M and Tripathi RS. Traps and trapping. In: Prakash and Ghosh PK (ed) Rodents in Indian Agriculture, Vol. I, Scientific Publishers, Jodhpur, 1992; 585–594.  Back to cited text no. 25
    
26.
Taylor KD, Hammond LE, and Quy RJ. The reactions of common rats to four types of live- capture trap. Journal of Applied Ecology 1974; 11: 453–459.  Back to cited text no. 26
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

Top
 
  Search
 
    Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
 Related articles
    Access Statistics
    Email Alert *
    Add to My List *
* Registration required (free)  

  Material & M...
  In this article
Abstract
Introduction
Results
Discussion
References
Article Figures
Article Tables

 Article Access Statistics
    Viewed437    
    Printed0    
    Emailed0    
    PDF Downloaded10    
    Comments [Add]    

Recommend this journal