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Medical Entomology Consulting

Population size and distribution of geometricus (brown widow) with information on other common of Guam

Submitted to:

36 MED/SGOAH - Andersen AFB, Guam

Consultative Letter #: IERA-DO-BR-CL-2001-0062

Prepared by:

Detachment 3, AFIERA/CDM Kadena AB, Okinawa

12July2001

DEPARTMENT OF THE AIR FORCE DETACHMENT 3, AIR FORCE INSTITUTE FOR ENVIRONMENT, SAFETY, AND OCCUPATIONAL HEALTH RISK ANALYSIS (AFIERA) (AFMC) APO AP 96368-5213

MEMORANDUM FOR 36 MED/SGOAH 12July01

FROM: Detachment 3, AFIERA/CDM Attn: Lt. Mary Ann Haberman, DSN 634-2639 Unit 5213 APO AP 96368-5213

Subject: Population size and distribution of introduced Brown Widow (Latrodectus geometricus) and the threat to military personnel and dependents on Andersen AFB, Guam, USA. Consultative Letter, IERA-DO-BR-CL-2001-0062

1. Introduction: An exotic species of spider, Latrodectus geometricus, (the brown widow) belonging to the widow family Theridiidae was recently found near the AMC Terminal on Andersen Air Force Base, Guam. The recent introduction of the brown widow more than likely originated from one or more of the cargo flights into the AMC terminal. As this spider species is not known to occur on the island, a spider survey was conducted to determine the population size and distribution of the brown widow. This report details the population size and present locations of these spiders, and provides information on other common spiders of Guam. Recommendations are provided to minimize the already small risk of encounter with the brown widow and possible control measures. Extensive evidence of the brown widow was found in two isolated locations near the AMC Terminal and surrounding buildings. These spiders pose minimal threat to humans however, since the population in this location is large and widow populations are known to undergo extreme fluctuations, a management program is suggested and detailed in this report.

2. Survey Personnel and Contacts:

SSgt Kevin Richards 36th MED/SGOAH Arm Stephanie Cash 36th MED/SGOAH 1Lt Mary Ann Haberman Det 3, AFIERA

3. Background and Survey Techniques: a. There are four distinct terrestrial habitats on Guam and all provide differing habitats for insect and spider populations. Because of the differing habitats, several survey techniques were used to sample spider populations, (1.) The limestone forest is the natural forested area and grows only where limestone rock is present. Most of northern Guam was once covered with limestone forest, but at present the only remaining tracts are located along the rugged coastal cliff lines or on military installations. (2.) The wetlands, including streams, swamps, and ponds are also located throughout the island. Wetlands hold water for extended period of the year and are extremely fertile. These areas support a wide variety of plant and life which are able to sustain in saturated environments. (3.) The savanna, or grassland, is also an important landscape feature and occupies a large portion of southern Guam. The red clay soil in this area sustains a variety of grasses and mosses. (4.) The mangroves and estuaries of Guam consist of freshwater rivers and ocean water mixing to create brackish estuaries. The sheltered shorelines and mangroves provide ideal habitat for many kinds of , plants and insects/spiders. b. The highly variable habitat types on Guam provide rich diversity for local flora and fauna populations. Consequently, several survey techniques are required to successfully sample spider populations. The most useful method of spider collection for all of the habitat types is visual inspection/collection (Fig. 1). In the limestone forests, sticky traps were also places in locations where spiders are likely to be found. Sweep nets were also used to collect from the undergrowth and in the grassy Savanna habitat. c. Buildings and other man-made structures provide a sizable habitat for these opportunistic spiders so an extensive survey was conducted in/around the buildings at Andersen Air Force Base. A visual survey was performed at the AMC Terminal beginning with the main building and the surrounding structures working outward in concentric circles. Housing areas were also intensely surveyed as these spiders also be found in the crates transported into housing areas.

Figure 1. Inspection/collection survey method

4. Discussion: a. Spiders of Medical Importance on Guam: There have been 30 families of spider documented on Guam to date and of those, only two venomous spider species capable of biting humans were collected on Andersen Air Force Base and the surrounding area. Latrodectus geometricus (brown widow) of the family Theridiidae (comb footed spiders), and Chiracanthium spp. (yellow sac spider) of the family Clubididae (hunting spiders) are both capable of biting humans. Of the two medically important spiders, only the yellow sac spider has necrotizing capable of causing lesions. Though the brown widow venom does not cause necrotizing lesions on the skin, the venom can cause muscle cramping and pain at the site of the bite. Details on these medically important spiders, along with descriptions of other locally common spiders are given below. 1. Family Theridiidae: This very large family contains spiders found throughout the world with 24 genera and nearly 2400 species. The Genus Lactrodectus containing the brown widows belongs to this family with more than 10 species found worldwide. Though none are native to Guam, the brown widow, Latrectus geometricus is now found in an isolated area on Andersen Air Force Base. The area directly behind the AMC Terminal provides a multitude of prime habitats for brown widows and a very large population was found in the A/C unit near the flight line (Fig. 2). Nearly every instar (developmental stage) was represented in the survey indicating that the population is well established and has likely been in place for more than one season. The best way to determine the age of a population of spiders is to investigate the genetic diversity of spiders found in close proximity. The more genetic diversity, the longer the population has been in place. The results of a genetic diversity study are pending. The life history and biology of these spiders is well documented. Evidence of spiders such as webbing, egg cases and brown widows themselves are found in dark, out of the way places including storage sheds, brickwork, eaves, discarded building material, storm sewers, down spouts, outdoor lighting, and under outdoor furniture. These spiders are nocturnal and construct an irregular, unorganized, loosely woven web 1-6 feet above the ground. The web usually contains raisin sized “cottony” egg sacs, grass clippings and often other debris. Brown widows are light brown in color and have a reddish hour-glass marking on the underside of their abdomen (Fig. 3). Female brown widows have a series of markings on the sides of their abdomen and bands/rings on their legs (Fig. 4). Abdominal markings and leg bands become less apparent in older females.

Figure 2. A/C Unit behind the AMC Terminal.

Figure 3. Reddish hour-glass marking on the Figure 4. Dark bands on the joints underside of the abdomen on a female brown of the legs on a female brown widow, widow, Latrodectus geometricus . Latrodectus geometricus.

Given the life history of the brown widow, the risk they pose to humans is minimal. In general, brown widows bite when trapped against the skin either by reaching under objects where the spider is hiding or when putting on clothing, gloves or shoes containing the spider. Latrodectus spiders are generally very timid and only bite as a last defense when they accidentally contact humans. Few bites are reported from immature or male widows, whose short fangs may not penetrate the skin. Symptoms from bites are systemic, spreading through the lymphatic system and usually start about 1-3 hours post-bite, whereupon the patient seeks treatment. The most common symptoms are intense pain, rigid board-like stomach muscles, muscle cramping, malaise, local sweating, nausea, oliguria, vomiting and hypertension. Although abdominal rigidity is one of the clinically diagnostic symptoms in many widow bites, it does not appear to be common in L. hasselti (red-back) bites. If left untreated, Latrodectus bite symptoms usually last 3-5 days. Calcium gluconate and/or may be administered to releive or counteract symptoms. Apparently, some local hospitals carry the antivenom, though their use is controversial due to potential for allergic reactions to the horse-serum antivenom. Historically, widow bites have killed approximately 5% of its human victims. Despite the effects widow venom has on muscle activity, there is no long term effect to the human body. The bite site may have localized swelling and two fang marks may be seen where the skin was penetrated. In untreated cases, a rash may develop in several days. Diagnosis is more assured from the definitive systemic symptoms. 2. Family Clubionidae: Yellow Sac Spiders (Chiracanthium spp.) are found worldwide and are typically medium-sized (6-10 mm body length) and pale yellow with black cheilcerae (housing for the fangs). There are over 1500 genera of sac spiders found worldwide with highly variable reactions to their bites. These spiders are commonly found in leaf litter or walking about on foliage. They do not use a web in prey capture; they actively hunt prey and can be observed in gardens or along the edge of vegetation. Those found in the Pacific area are nocturnal hunters that tend to be yellowish-orange in color. They spin silken retreats in curled up leaves or in crevices into which they return after hunting and when threatened. Yellow sac spiders rarely infest housing so the chance of encounter is slim. In other parts of the world, bites from these spiders have been reported to occur at night when spiders encounter a sleeping human. Many bites are painful at inception and can produce slightly necrotic wounds that usually heal in a short duration without severe scarring. Other symptoms that may accompany the bite from a yellow sac spider includes itching, shivering, vomiting and a slight fever. The symptoms are usually short in duration and subside in several days.

Figure 5. Yellow Sac Spider (Chiracanthium sp.) commonly found in/around housing areas and near the beaches.

b. OTHER SPIDERS: Though there are only two species that can be considered medically important, there are many other relatively harmless spider species present on Guam and which could be encountered by humans. 1. Family Araneidae: Typical Orb Weavers including numerous species of both Nephila and Argiope are found throughout the island including housing and surrounding buildings. Banana spiders (Nephila spp.) (Fig. 6) construct large orb webs in the shaded areas of the forests and are easily recognized by the pronounced tufts of hair on their legs. They are usually dark brown with yellow and white marking on the carapace. Garden spiders (Argiope spp.) (Fig. 7) also construct an orb web but also include a distinctive stabilimentum (zig zag) near the center of the web. Their carapace is usually covered with silvery hair and is marked with yellow and black stripes. There is a great deal of variability within this genus with many different color variations and body shapes.

Figure 6. Nephila sp. Figure 7. Argiope sp.

2. Family : These long legged Cellar spiders, represented on Guam by Pholcus phalangioides, are common throughout housing and other buildings on Andersen Air Force Base. This family of spiders is relatively small but several of the species are extremely common. These spiders are found worldwide and are considered beneficial even though the webs they make are often unsightly. These spiders are opportunistic and will build their webs in nearly any location and are capable of withstanding extremely adverse conditions (Fig. 8). P. phalangioides are incapable of biting humans as their mouth parts are extremely small so they pose no threat to humans.

Figure 8. Pholcus phylangoides

3. Family Salticidae: The other, and even more common, species of spider in housing are those belonging to the Family Salticidae or the Jumping spiders (Fig. 9). These spiders belong to the largest family of spiders and are found around the world. They are easily recognized by the pattern of their large eyes and the brightly colored marking on their carapace. These spiders have extremely keen vision and are often seen hunting their prey in broad daylight. Jumping spiders are known for their jumping ability and can perform amazing leaps when stalking prey. They do not construct a web for prey capture, however, they build a small silken retreat into which the flee when threatened, consuming a prey item, molting, or spending the night. Again these spider are considered beneficial because they capture unwanted/harmful insects in and around housing.

Plexippoides sp. Phintella sp. Sitticus sp. Phintella sp. Figure 9. Several species of Salticid spider commonly found in housing areas.

4. Sparassidae: Giant spiders, locally named the , are commonly found at the beach areas, on ranches, and in housing. These spiders do not build a web to capture prey rather they hunt prey at night. They are yellow to brown in color and have tiny hairs covering their carapace (Fig. 10). Huntsman lay their large egg cases attached to the vegetation in the woods (Fig. 11) and sire 50- 100 offspring each season. These spiders are large and may look intimidating, but in fact they are quite docile.

Figure 10. Giant Crab Spider Figure 11. Huntsman egg case ( sp.) locally called the Huntsman.

5. Other Families: Guam is home to many other families of spiders each containing numerous species. Other families represented include the Long Jawed Orb Weavers (Tetragnathidae) (Fig. 12), Wolf spiders (Lycosidae) (Fig. 13), Lynx spiders (Oxyopidae) (Fig.14), Spitting Spiders (Scytodidae) (Fig. 15), Pirate Spiders (Therididae) (Fig. 16) and the parasitic spiders (Uloboridae) (Fig.17), all of which do not pose a threat to humans.

Figure 12. Tetrignathidae Figure 13. Lycosidae Figure 14. Oxyopidae (Long Jawed Ord Weavers) (Wolf Spiders) (Lynx Spiders)

Figure 15. Scytodidae Figure 16. Therididae Figure 17. Uloboridae (Spitting Spiders) (Pirate Spiders) (Parasitic Spiders)

c. Toxicologically: There is far more diversity in spider than in the venoms of Hymenoptera (ants, bees and wasps) and scorpions, so the correct identification of spider bites has special significance. As most spiders cannot penetrate human skin and/or the probability of encounter and being bitten is remote, the venom characteristics of most species are unknown. Spiders are rarely correctly identified by bite victims or their physicians and have an undeserved poor reputation. Fear of spiders (arachnophobia) is very common, varying from mild disgust to mass hysteria. This is exacerbated by news reports that over-emphasize the dangers of spider bites far out of proportion to the actual threat that they pose, especially in relation to many of our daily activities. This validation by the media spills over to medical diagnoses where physicians ascribe “potential ” to many lesions of unknown origin. Widow spider venom is a neural and would not cause necrotic lesions. Toxicological testing at Ryukyu University, Okinawa, Japan, on brown widow venom shows that bites from this species are less harmful due to the smaller amount of venom released (and smaller fangs) when compare with other widow species.

5. Results and Conclusions: Of the various methods of spider collection, the most effective was visual inspection and collection. Eighty-nine spiders were collected representing 11 families. This survey, coupled with the historical data presents a relatively accurate picture of the common spiders found on Guam. Of the thirty sticky traps placed in various locations in housing areas, scattered in the Limestone Forest, and in/around the AMC Terminal, no spider were caught. Upon intense visual inspection both during the day and at night, numerous jumping spiders, huntsman, and other harmless hunting type spiders were located. All of these spiders are unlikely to bite humans and therefore present minimal risk. A variety of other organisms were caught on the sticky traps placed in the Limestone Forest including several species of Gecko, , bugs, moths, ants and flies. Of those sticky traps set in and around the building, ants, cockroaches, millipedes and earwigs were caught. None of the caught would cause skin or other health problems. Evidence of brown widows or the spiders themselves were found in only two isolated areas on Andersen Air Base. These spiders have never been recorded on the island and were not found off base during this survey. Brown widows, their webs and egg cases were found at the AMC Terminal and under a set of concrete steps at the loading docks of the Commissary (Fig. 18). No brown widows were found in housing or the building in/near the housing areas. No evidence of these spiders was found at the numerous playgrounds or other recreational areas. Since these spiders rely on wind to carry them from place to place (), they have remained in a small isolated area. The prevailing winds (arrows on Figure 18) are such that the spider population has effectively been pinned next to the building with natural barriers on all sides. The spider population has a building bordering three sides and a large open field on the third over which they cannot balloon. There is also a large field directly across the street from the AMC terminal, which has likely prevented their ballooning to other buildings in the area. The brown widows found at the Commissary were probably accidentally introduced via mechanical transportation and likely have not had the opportunity to establish a population there.

X X

Figure 18. AMC Terminal at Andersen Air Force Base. X marks the two locations where evidence of brown widows was found.

6. Recommendations: In general, widow spiders are known to inhabit packing material, cargo, and household goods. Widows could potentially be accidentally introduced/imported from other areas of the world where they commonly occur. In particular, the relatively undisturbed, dark, and protected areas at the AMC terminal could provide an ideal habitat for medically important spiders (including brown widows) and other arthropods. Numerous species of the cobweb and hunting spiders were observed and/or collected during visual inspections of the AMC terminal and surrounding area (including housing). Of the spiders observed at the AMC terminal, a very large percentage was positively identified as Latrodectus geometricus, the brown widow. Employees working at the AMC terminal have a slim chance of being bitten and seriously injured from brown widow spiders. Even though the risk to employees is low, the size of the population in this area alone is high enough to warrant control measures. I suggest that an integrated spider management program be implement to include the following: a. The area around the AMC terminal should be cleaned (vacuum, physical removal or high pressured steam). b. Pesticide fog should be introduced into the area in and around the motors for the A/C units behind the terminal. c. Residual pesticides should be applied to the grassy areas where the infestations have been documented and in the grassy fields behind the AMC Terminal and across the street. d. Aerosol pray should be used to control juveniles and egg cases in the cracks and crevices where the pesticide cannot reach. e. Inspections should be performed periodically in accordance with a scheduled plan to determine the effectiveness of control measures.

7. Contact me at DSN: 634-2639, or via e-mail at [email protected] if there are any questions regarding this report.

Mary Ann Haberman, 1Lt, USAF, BSC Chief Medical Entomology Branch

cc: 36 MDOS/SGOAB 36 CES/CEORE

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