The Gulf Coast tick, Amblyomma maculatum
Our trapping efforts indicated that the vector of this disease is the Gulf Coast tick, Amblyomma maculatum.
Historically, Amblyomma maculatum has been distributed in areas described to be within approximately 160 km from the Gulf Coast of Mexico and the Atlantic Coast (Bishopp and Trembley 1945). The inland distribution of Amblyomma maculatum appears to fluctuate between wet and dry years, indicating its dependence on rainfall, humidity and temperature. A permanent population of Amblyomma maculatum also exists in Kansas (Brillhart et al. 1994) and Oklahoma (Barker et al. 2004). Outside of the U.S., Amblyomma spp. have been documented in Peru, Paraguay, Mexico, Ecuador, Chile, Brazil, Uruguay, Argentina, Jamaica, and Colombia (Cooley and Kohls 1944). Amblyomma maculatum ticks are found on hosts or in vegetation. They seek out areas with high humidity, good shade, shelter, and little wind to avoid desiccation (Singh 2012). Habitat includes buckbrush, blackberry brush, lowland prairie, and sumac. Although populations of Amblyomma maculatum are found in blackjack oak forests, ravine and upland prairie habitats, these habitats are not preferred (Semtner and Hair 1973).
Historically, Amblyomma maculatum has been distributed in areas described to be within approximately 160 km from the Gulf Coast of Mexico and the Atlantic Coast (Bishopp and Trembley 1945). The inland distribution of Amblyomma maculatum appears to fluctuate between wet and dry years, indicating its dependence on rainfall, humidity and temperature. A permanent population of Amblyomma maculatum also exists in Kansas (Brillhart et al. 1994) and Oklahoma (Barker et al. 2004). Outside of the U.S., Amblyomma spp. have been documented in Peru, Paraguay, Mexico, Ecuador, Chile, Brazil, Uruguay, Argentina, Jamaica, and Colombia (Cooley and Kohls 1944). Amblyomma maculatum ticks are found on hosts or in vegetation. They seek out areas with high humidity, good shade, shelter, and little wind to avoid desiccation (Singh 2012). Habitat includes buckbrush, blackberry brush, lowland prairie, and sumac. Although populations of Amblyomma maculatum are found in blackjack oak forests, ravine and upland prairie habitats, these habitats are not preferred (Semtner and Hair 1973).
Amblyomma maculatum ticks have a one year hemimetabolous life cycle consisting of egg, larval, nymphal and adult life stages (Fleetwood 1985). Along the greater Gulf Of Mexico U.S. coast and the Atlantic coast, larvae are found on hosts from mid-June to early September, with the peak in early July, and a second smaller peak in early August. Nymphs are found on their primary hosts between early July and early October, with a peak in early August and a second smaller peak in early September. Adult ticks have an abundance peak from late May to early July (Semtner and Hair 1973). In the Gulf Coastal region of Texas, larvae and nymph Amblyomma maculatum ticks have an activity peak from November to February, and sometimes as late as April due to milder winters (Teel et al. 1988). Adult Amblyomma maculatum ticks have activity peaks from May through August (Teel et al 1998). Amblyomma maculatum ticks follow a polygynandrous mating system. Males use pheromones to attract females for mating while on a host. The Haller’s organ, an olfactory organ found on the distal tarsi of coxa I, is used to perceive these pheromones. The mating process involves the male transferring sperm to the female from his mouthparts to the female’s vagina via a spermatophore. Males can mate multiple times. Before a female mates, she partially engorges herself. After the mating process, she fully engorges herself and detaches from the host for oviposition. Females use the Gené’s organ to waterproof eggs twice during oviposition and usually lay eggs in leaf litter (Teel et al. 1998). Oviposition follows a circadian rhythym and depends on the blood meal acquired before beginning. Larger blood meals yield higher numbers of eggs deposited. Females die after depositing eggs (Singh 2012).
Larval Amblyomma maculatum are about 0.17 mm in length. The basis capitulum is wide, sub-triangular, and has lateral points extending beyond the scapulae. The posterior capitulum is rounded posteriorly, smooth, shining, faintly shagrened, and impunctate. The palpi are short, smooth, and have a few, fine hairs. The hypostome is spatulate and rounded terminally. The scutum is broadly rounded behind, smooth, shining, shagrened, and impunctate. It is widest near the center of the dorsal region. There are nearly parallel shallow cervical grooves. Each coxa has a single, short, triangular spur. The spur on coxa I is the largest, and the spurs on coxa II and III are progressively smaller. Coxae lack hairs (Cooley and Kohls 1944).
The idiosoma of the Amblyomma maculatum nymph is narrow, 1.44 mm in length, and 0.93 mm in width. When it is not engorged it is pyriform. The scutum is about ⅓ body length. It is slightly wider than it is long, broadly rounded behind, and widest near the mid-posterior end. The scapulae are rounded and covered by the sides of the basis capituli. There are eyes present, and they are flat and pale. The scutum is free of hair. Anteriorly, the cervical grooves are deep, and become shallow as they continue near the postero-lateral margins. There are only a few punctuations on the scutum. The basis capitulum is triangular. The lateral points of the capitulum protrude outside the scapulae. There are two distinct retrograde spurs on the ventral surface of the basis capitulum. The surface of the capitulum is nearly flat, smooth, shining, and impunctate. The palpus is long, and widest at the suture between 2 and 3, and narrow at the base. There are a few moderately long hairs on the capitulum. The hypostome is spatulate and rounded terminally. The legs of the nymphs are shorter and smaller than legs of adults. There are no spurs on the tarsi or metatarsi. Coxa I bears a moderate internal spur and coxa II has one short, broad, flat spur. Coxae III and IV are smooth and shiny with few hairs and lack spurs. The spiracular plate is large and flat, with a little sclerotized frame (Cooley and Kohls 1944).
Adult Amblyomma maculatum possess a sub-rectangular shaped basis capitulum that is longer than that of other species. The idiosoma is ovoid with anterior narrowing and posterior widening. Size ranges from 3.40mm to 5.00mm long and 2.40mm to 3.00mm wide. They also possess slightly convex eyes and ornate scutums. The scapulae are long and pointed. The legs are long and large. The palpi are long and widest at article three. There are a few short hairs. The hypostome is long and notched apically. Leg I is longer but smaller than the others. There are apical spurs on tarsi II, III, and IV, but not on tarsus I. There are long, paired terminal spurs on metatarsi II, III, and IV. Coxa I has a very short internal spur and a long, pointed external spur. Coxa II has a broad, flat, short spur. Coxae III and IV have similar spurs to coxa II, but they get progressively smaller. The genital aperture is at a level between coxae II and III (Cooley and Kohls 1944).
Adult female Amblyomma maculatum body size ranges from 3.70 mm to 4.40 mm in length, and from 2.40 mm to 2.85 mm in width. Engorged females may grow to be as long as 18.00 mm in length, and to 13.00 mm in width. The marginal groove is complete and continuous across all the festoons. The festoons often have a small, terminal nub visible from above. The scutum is less than half of the body length. It is ornate, with contrasting light and dark patterns. The shape of the scutum is sub-triangular, narrowed posteriorly, and rounded terminally, with a very convex antero-lateral border. The cervical grooves are shallow, somewhat deep anteriorly, and disappear posteriorly. There are many punctuations of large and small size, with larger ones anteriorly. The postero-lateral corners protrude slightly. The surface of the capitulum is smooth, shiny, and punctuate. The porose areas are large, convex, and slightly divergent anteriorly. The spiracular plate is large, concave, and has a well-sclerotized frame (Cooley and Kohls 1944).
Adult male Amblyomma maculatum are slightly larger than females, ranging from 3.40 mm to 5.00 mm in length and 2.40 to 3.00 mm in width. The scutum is often mildly concave between the eyes. It has deep, complete lateral grooves. The festoons are long and well-defined. Ventral scutes extend over the margin and can be seen from above. Cervical grooves are deep anteriorly and shallow posteriorly. There are long scapulae present with a deep interval between them. The male scutum is decorated with lineal, connected spots of golden white. The postero-lateral corners protrude a little and form a short cornua. The dorsal surface of the capitulum is convex, somewhat irregular, and punctuate. The spiracular plate is large and somewhat convex, with a well-sclerotized frame (Cooley and Kohls 1944).
The idiosoma of the Amblyomma maculatum nymph is narrow, 1.44 mm in length, and 0.93 mm in width. When it is not engorged it is pyriform. The scutum is about ⅓ body length. It is slightly wider than it is long, broadly rounded behind, and widest near the mid-posterior end. The scapulae are rounded and covered by the sides of the basis capituli. There are eyes present, and they are flat and pale. The scutum is free of hair. Anteriorly, the cervical grooves are deep, and become shallow as they continue near the postero-lateral margins. There are only a few punctuations on the scutum. The basis capitulum is triangular. The lateral points of the capitulum protrude outside the scapulae. There are two distinct retrograde spurs on the ventral surface of the basis capitulum. The surface of the capitulum is nearly flat, smooth, shining, and impunctate. The palpus is long, and widest at the suture between 2 and 3, and narrow at the base. There are a few moderately long hairs on the capitulum. The hypostome is spatulate and rounded terminally. The legs of the nymphs are shorter and smaller than legs of adults. There are no spurs on the tarsi or metatarsi. Coxa I bears a moderate internal spur and coxa II has one short, broad, flat spur. Coxae III and IV are smooth and shiny with few hairs and lack spurs. The spiracular plate is large and flat, with a little sclerotized frame (Cooley and Kohls 1944).
Adult Amblyomma maculatum possess a sub-rectangular shaped basis capitulum that is longer than that of other species. The idiosoma is ovoid with anterior narrowing and posterior widening. Size ranges from 3.40mm to 5.00mm long and 2.40mm to 3.00mm wide. They also possess slightly convex eyes and ornate scutums. The scapulae are long and pointed. The legs are long and large. The palpi are long and widest at article three. There are a few short hairs. The hypostome is long and notched apically. Leg I is longer but smaller than the others. There are apical spurs on tarsi II, III, and IV, but not on tarsus I. There are long, paired terminal spurs on metatarsi II, III, and IV. Coxa I has a very short internal spur and a long, pointed external spur. Coxa II has a broad, flat, short spur. Coxae III and IV have similar spurs to coxa II, but they get progressively smaller. The genital aperture is at a level between coxae II and III (Cooley and Kohls 1944).
Adult female Amblyomma maculatum body size ranges from 3.70 mm to 4.40 mm in length, and from 2.40 mm to 2.85 mm in width. Engorged females may grow to be as long as 18.00 mm in length, and to 13.00 mm in width. The marginal groove is complete and continuous across all the festoons. The festoons often have a small, terminal nub visible from above. The scutum is less than half of the body length. It is ornate, with contrasting light and dark patterns. The shape of the scutum is sub-triangular, narrowed posteriorly, and rounded terminally, with a very convex antero-lateral border. The cervical grooves are shallow, somewhat deep anteriorly, and disappear posteriorly. There are many punctuations of large and small size, with larger ones anteriorly. The postero-lateral corners protrude slightly. The surface of the capitulum is smooth, shiny, and punctuate. The porose areas are large, convex, and slightly divergent anteriorly. The spiracular plate is large, concave, and has a well-sclerotized frame (Cooley and Kohls 1944).
Adult male Amblyomma maculatum are slightly larger than females, ranging from 3.40 mm to 5.00 mm in length and 2.40 to 3.00 mm in width. The scutum is often mildly concave between the eyes. It has deep, complete lateral grooves. The festoons are long and well-defined. Ventral scutes extend over the margin and can be seen from above. Cervical grooves are deep anteriorly and shallow posteriorly. There are long scapulae present with a deep interval between them. The male scutum is decorated with lineal, connected spots of golden white. The postero-lateral corners protrude a little and form a short cornua. The dorsal surface of the capitulum is convex, somewhat irregular, and punctuate. The spiracular plate is large and somewhat convex, with a well-sclerotized frame (Cooley and Kohls 1944).
Amblyomma maculatum is a three host tick (Singh 2012). Nymphs and larvae primarily feed on birds and small mammals. Avian hosts include bobwhite quail, grasshopper sparrows, meadowlarks, Brewer’s blackbirds, red-winged blackbirds, towhees, field sparrows, house wrens, brown thrashers, mockingbirds, blue jays, and loggerhead shrikes. During the fall and winter months, meadowlarks and bobwhite quail are the most important hosts for larvae and nymphs (Cooley and Kohls 1944). Mammalian hosts include cotton rats, deer mice, foxes, jackrabbits, eastern fox squirrels, eastern gray squirrels, lambs and roof rats. Adults parasitize a variety of large animals. Adult Amblyomma maculatum primarily feed on cattle. Herefords and Angus cattle seem to be favored over Brahman cattle. Brahman calves are infested with approximately half the amount of ticks as Hereford or Angus calves are (Semtner and Hair 1973). Adults also feed on other livestock such as sheep, horses, goats; meso to large sized mammals such as squirrels, dogs, and wolves; as well as humans (Cooley and Kohls 1944). Amblyomma maculatum vectors Hepatozoon americanum, the American canine hepatozoonosis, and is a vector for a spotted fever, Rickettsia parkeri (EOL, accessed 10-22-2014).
Literature Cited
Barker, R. W., A. A. Kocan, S. A. Ewing, R. P. Wettemann, and M. E Payton. 2004. Occurrence of the Gulf Coast tick (Acari: Ixodidae) on wild and domestic mammals in North-Central Oklahoma. J. Med. Entomol. 41: 170-178.
Bishopp, F. C., and H. L. Trembley. 1945. Distribution and hosts of certain North American ticks. J. Parasitol. 31: 1-54.
Brillhart, D. B., L. B. Fox, and S. J. Upton. 1994. Ticks (Acari: Ixodidae) collected from small and medium-sized Kansas mammals. J. Med. Entomol. 31: 500-504.
(CDC) Centers for Disease Control. 2014. Distribution. http://www.cdc.gov/ticks/geographic_distribution.html
Cooley, R. A., and G. M. Kohls. 1944. The genus Amblyomma (Ixodidae) in the United States. J. Parasitol. 30: 77-11.
(EOL) Encyclopedia of Life. Amblyomma maculatum. http://eol.org/pages/514923/overview
Fleetwood, S. C. 1985. The environmental influences in selected vegetation microhabitats on the various life stages of Amblyomma maculatum Koch (Acari: Ixodidae). PhD Dissertation, Texas A&M University, College Station.
Semtner, P. J., and J. A. Hair. 1973. Distribution, seasonal abundance, and hosts of the Gulf Coast Tick in Oklahoma. ANN ENTOMOL SOC AM. 66: 1264-1268.
Teel, P. D., S.C. Fleetwood, S. W. Hopkins, and D. Cruz. 1988. Ectoparasites of Eastern and Western meadowlarks from the Rio Grande plains of south Texas. J. Med. Entomol. 25: 32-38.
Teel, P. D., S.W. Hopkins, W. A. Donahue, and O. F. Strey. 1998. Population dynamics of immature Amblyomma maculatum and other ectoparasites on meadowlarks and northern bobwhite quail resident to the coastal prairie of Texas.J. Med. Entomol. 35: 483-488.
University of Rhode Island TickEncounter Resource Center. 2014. Tick Identification. http://www.tickencounter.org/tick_identification/gulf_coast_tick
Bishopp, F. C., and H. L. Trembley. 1945. Distribution and hosts of certain North American ticks. J. Parasitol. 31: 1-54.
Brillhart, D. B., L. B. Fox, and S. J. Upton. 1994. Ticks (Acari: Ixodidae) collected from small and medium-sized Kansas mammals. J. Med. Entomol. 31: 500-504.
(CDC) Centers for Disease Control. 2014. Distribution. http://www.cdc.gov/ticks/geographic_distribution.html
Cooley, R. A., and G. M. Kohls. 1944. The genus Amblyomma (Ixodidae) in the United States. J. Parasitol. 30: 77-11.
(EOL) Encyclopedia of Life. Amblyomma maculatum. http://eol.org/pages/514923/overview
Fleetwood, S. C. 1985. The environmental influences in selected vegetation microhabitats on the various life stages of Amblyomma maculatum Koch (Acari: Ixodidae). PhD Dissertation, Texas A&M University, College Station.
Semtner, P. J., and J. A. Hair. 1973. Distribution, seasonal abundance, and hosts of the Gulf Coast Tick in Oklahoma. ANN ENTOMOL SOC AM. 66: 1264-1268.
Teel, P. D., S.C. Fleetwood, S. W. Hopkins, and D. Cruz. 1988. Ectoparasites of Eastern and Western meadowlarks from the Rio Grande plains of south Texas. J. Med. Entomol. 25: 32-38.
Teel, P. D., S.W. Hopkins, W. A. Donahue, and O. F. Strey. 1998. Population dynamics of immature Amblyomma maculatum and other ectoparasites on meadowlarks and northern bobwhite quail resident to the coastal prairie of Texas.J. Med. Entomol. 35: 483-488.
University of Rhode Island TickEncounter Resource Center. 2014. Tick Identification. http://www.tickencounter.org/tick_identification/gulf_coast_tick