J.
Med. Entomol.
7 November 1978
Vol. 15, no. I: 84-85
PRESUMED DIROFILARIA IMMITIS INFECTIONS IN NATURAL MOSQUITO POPULATIONS OF CONNECTICUT Abstract: During the summers of 1976 and 1977. 3294 ver· tebrate host·seeking mosquitoes were captured by the human·bait method in areas where dog heartworm was known to occur. Following dissections of ovaries and other internal organs. specimens were age·graded by the Polovodova method and examined for filarial worms. "Sausage-stage,"!ate 2nd-stage, and (or) L~-stage filarial larvae were found in 46 (1.4%) of Aedes canadensis, Ae. excrueians, Ae. stimulans, vexans, and PsoroPhora ferox. Filarial
Ae. sol/ieitans,
Ae.
Combined hematologic and necropsy surveys of Con· necticut dogs revealed that dirofilariasis occurs in both urban and suburban areas (Hirth, Huizinga & Nielsen, 1966,]. Am. Vet. Med. Assoc. 148: 1508-16). According to Ludlam, Jackowski & Ouo (1970, ]. Am. Vet. Med. Assoc. 157: 1354-59). numerous mosquito species are suspected vectors of the dog heartworm parasite, Dirofilaria immitis (Leidy), but this hypothesis is based almost exclusively on laboratory studies. Since little is known about the natural occurrence of D. immitis in feral mosquitoes, a survey for this parasite was initiated. This communication reports the presence of infectious-stage (L5) D. immitis, late 2nd·stage, and "sausage·stage" filarial worms in 6 common mosquito species. Studies were conducted in southern Connecticut at Guilford and Mt. Carmel. The former includes extensive salt marshes bordering residential areas, and the latter consists of woodlands adjacent to human dwellings. Discussions with residents in these towns and veterinarians established that dog heartworm occurred in neighborhoods contiguous with the designated sampling sites.
TABLE 1. Occurrence of early and late 2nd-stage larvae and (or) infective filarial worms in host-seeking mosquitoes at Guilford and Mt. Carmel, Connecticut during June, July, and August 1976 and 1977.
SPECIES Ae. abserratus Ae. canadensis Ae. cantator Ae. excrncians Ae. sollicitans Ae. stimulans Ae. triseriatus Ae. vexans Ps·ftrox
Totals
TOTAL~~ CAUGHT 303 509 385 225 585 562 323 242 353 3487
No. EXAMINED N" 148 215 193 91 313 294 176 128 185 1743
No. AND(%)* WITHFILARIAE
P
Total
N
P
123 268 170 123 245 247 132 95 148 1551
271 483 363 214 558 541 308 223 333 3294
0 3(1.4) 0 0 4(1.3) 2(0.7) 0 0 0 9(0.5)
0 12(4.5) 0 5(4.1) 7(2.9) 8(3.2) 0 2(2.1) 3(2.0) 37(2.8)
*%=total ~~ having filariae/total ~~ examined in species age group. **N = Nulliparous, P=Parous.
No. PARAStTES PER INFECTED~
Total
x
Range
15(3.1)
4.8
2-8
5(2.3) 11(2.0) 10(1.9)
3.2 4.7 5.0
2-4 2-8 1-9
2(0.9) 3(0.9) 46(1.4)
2.0 4.7
2-7
Downloaded from http://jme.oxfordjournals.org/ by guest on June 5, 2016
worms occurred in nulliparous as well as parous mosquitoes. Although Ae. canadensis appears to be an important potentia] vector, the complete development of Dirofilaria immitis to the infectious stage in 3 other mosquito species suggests that mosquitoes of several species are probably involved in dog heartworm transmission in the northeastern United States.
Vertebrate host-seeking mosquitoes were captured with an aspirator as they attempted to bite me. Collections were made twice a week between 0900 and 1800 h from late May through September 1976, and from late May through mid-August 1977. Ovaries were removed from freshly killed specimens in physiological saline, and parity was determined by Polovodova's method (in Detinova, 1962, World Health Organ., Geneva, 216 p.). Malpighian tubules were extracted, placed in physiological saline, teased apart, and microscopically examined for "sausage· stage" and late 2nd-stage larvae; insect thoraces and cephalic areas were dissected and examined to detect infective larvae. Dissections were performed on 3294 mosquitoes. TABLE 1 shows that filarial worms were found in 46 (1.4%) vertebrate host-seeking Aedes canadensis (Theobald), Ae. excrucians (Walker), Ae. stimulans (Walker), Ae. sollt'ct'tans (Walker), Ae. vexans (Meigen), and PsoroPhora ferox (Humboldt). Melanized "sausage-stage" larvae were recovered from 3 Ae. sollict'tans. I~.c!«
Med. Entomol.
7 November 1978
Vol. 15, no. I: 84-85
PRESUMED DIROFILARIA IMMITIS INFECTIONS IN NATURAL MOSQUITO POPULATIONS OF CONNECTICUT Abstract: During the summers of 1976 and 1977. 3294 ver· tebrate host·seeking mosquitoes were captured by the human·bait method in areas where dog heartworm was known to occur. Following dissections of ovaries and other internal organs. specimens were age·graded by the Polovodova method and examined for filarial worms. "Sausage-stage,"!ate 2nd-stage, and (or) L~-stage filarial larvae were found in 46 (1.4%) of Aedes canadensis, Ae. excrueians, Ae. stimulans, vexans, and PsoroPhora ferox. Filarial
Ae. sol/ieitans,
Ae.
Combined hematologic and necropsy surveys of Con· necticut dogs revealed that dirofilariasis occurs in both urban and suburban areas (Hirth, Huizinga & Nielsen, 1966,]. Am. Vet. Med. Assoc. 148: 1508-16). According to Ludlam, Jackowski & Ouo (1970, ]. Am. Vet. Med. Assoc. 157: 1354-59). numerous mosquito species are suspected vectors of the dog heartworm parasite, Dirofilaria immitis (Leidy), but this hypothesis is based almost exclusively on laboratory studies. Since little is known about the natural occurrence of D. immitis in feral mosquitoes, a survey for this parasite was initiated. This communication reports the presence of infectious-stage (L5) D. immitis, late 2nd·stage, and "sausage·stage" filarial worms in 6 common mosquito species. Studies were conducted in southern Connecticut at Guilford and Mt. Carmel. The former includes extensive salt marshes bordering residential areas, and the latter consists of woodlands adjacent to human dwellings. Discussions with residents in these towns and veterinarians established that dog heartworm occurred in neighborhoods contiguous with the designated sampling sites.
TABLE 1. Occurrence of early and late 2nd-stage larvae and (or) infective filarial worms in host-seeking mosquitoes at Guilford and Mt. Carmel, Connecticut during June, July, and August 1976 and 1977.
SPECIES Ae. abserratus Ae. canadensis Ae. cantator Ae. excrncians Ae. sollicitans Ae. stimulans Ae. triseriatus Ae. vexans Ps·ftrox
Totals
TOTAL~~ CAUGHT 303 509 385 225 585 562 323 242 353 3487
No. EXAMINED N" 148 215 193 91 313 294 176 128 185 1743
No. AND(%)* WITHFILARIAE
P
Total
N
P
123 268 170 123 245 247 132 95 148 1551
271 483 363 214 558 541 308 223 333 3294
0 3(1.4) 0 0 4(1.3) 2(0.7) 0 0 0 9(0.5)
0 12(4.5) 0 5(4.1) 7(2.9) 8(3.2) 0 2(2.1) 3(2.0) 37(2.8)
*%=total ~~ having filariae/total ~~ examined in species age group. **N = Nulliparous, P=Parous.
No. PARAStTES PER INFECTED~
Total
x
Range
15(3.1)
4.8
2-8
5(2.3) 11(2.0) 10(1.9)
3.2 4.7 5.0
2-4 2-8 1-9
2(0.9) 3(0.9) 46(1.4)
2.0 4.7
2-7
Downloaded from http://jme.oxfordjournals.org/ by guest on June 5, 2016
worms occurred in nulliparous as well as parous mosquitoes. Although Ae. canadensis appears to be an important potentia] vector, the complete development of Dirofilaria immitis to the infectious stage in 3 other mosquito species suggests that mosquitoes of several species are probably involved in dog heartworm transmission in the northeastern United States.
Vertebrate host-seeking mosquitoes were captured with an aspirator as they attempted to bite me. Collections were made twice a week between 0900 and 1800 h from late May through September 1976, and from late May through mid-August 1977. Ovaries were removed from freshly killed specimens in physiological saline, and parity was determined by Polovodova's method (in Detinova, 1962, World Health Organ., Geneva, 216 p.). Malpighian tubules were extracted, placed in physiological saline, teased apart, and microscopically examined for "sausage· stage" and late 2nd-stage larvae; insect thoraces and cephalic areas were dissected and examined to detect infective larvae. Dissections were performed on 3294 mosquitoes. TABLE 1 shows that filarial worms were found in 46 (1.4%) vertebrate host-seeking Aedes canadensis (Theobald), Ae. excrucians (Walker), Ae. stimulans (Walker), Ae. sollt'ct'tans (Walker), Ae. vexans (Meigen), and PsoroPhora ferox (Humboldt). Melanized "sausage-stage" larvae were recovered from 3 Ae. sollict'tans. I~.c!«
