Tools for delivering entomopathogenic fungi to malaria mosquitoes: effects of delivery surfaces on fungal efficacy and persistence.
BACKGROUND
Entomopathogenic fungi infection on malaria vectors increases daily mortality rates and thus represents a control measure that could be used in integrated programmes alongside insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). Before entomopathogenic fungi can be integrated into control programmes, an effective delivery system must be developed.


METHODS
The efficacy of Metarhizium anisopliae ICIPE-30 and Beauveria bassiana I93-825 (IMI 391510) (2 × 10(10) conidia m(-2)) applied on mud panels (simulating walls of traditional Tanzanian houses), black cotton cloth and polyester netting was evaluated against adult Anopheles gambiae sensu stricto. Mosquitoes were exposed to the treated surfaces 2, 14 and 28 d after conidia were applied. Survival of mosquitoes was monitored daily.


RESULTS
All fungal treatments caused a significantly increased mortality in the exposed mosquitoes, descending with time since fungal application. Mosquitoes exposed to M. anisopliae conidia on mud panels had a greater daily risk of dying compared to those exposed to conidia on either netting or cotton cloth (p < 0.001). Mosquitoes exposed to B. bassiana conidia on mud panels or cotton cloth had similar daily risk of death (p = 0.14), and a higher risk than those exposed to treated polyester netting (p < 0.001). Residual activity of fungi declined over time; however, conidia remained pathogenic at 28 d post application, and were able to infect and kill 73 - 82% of mosquitoes within 14 d.


CONCLUSIONS
Both fungal isolates reduced mosquito survival on immediate exposure and up to 28 d after application. Conidia were more effective when applied on mud panels and cotton cloth compared with polyester netting. Cotton cloth and mud, therefore, represent potential substrates for delivering fungi to mosquitoes in the field.
Mnyone
Ladslaus L
LL
Biomedical and Environmental Group, Ifakara Health Institute, P,O, Box 53, Off Mlabani Passage, Ifakara, Tanzania. llaurent@ihi.or.tz
Kirby
Matthew J
MJ
Lwetoijera
Dickson W
DW
Mpingwa
Monica W
MW
Simfukwe
Emmanuel T
ET
Knols
Bart G J
BG
Takken
Willem
W
Russell
Tanya L
TL
D000818:Animals; D000852:Anopheles / Q000382:microbiology*; D052982:Beauveria / Q000472:pathogenicity*; D052981:Metarhizium / Q000472:pathogenicity*; D009032:Mosquito Control / Q000379:methods*; D016019:Survival Analysis
Parasit Vectors. 2010 Mar 16;3(1):18
20233423
J Exp Biol. 2007 Aug;210(Pt 16):2939-47
17690243
Am J Trop Med Hyg. 2008 Jun;78(6):910-6
18541768
Parasit Vectors. 2010 Mar 01;3:12
20193085
J Am Mosq Control Assoc. 1991 Jun;7(2):176-9
1895075
Trop Med Int Health. 2008 Mar;13(3):430-3
18397404
Med Vet Entomol. 1987 Jan;1(1):37-51
2979519
Trop Med Int Health. 2006 Nov;11(11):1629-42
17054742
PLoS Comput Biol. 2009 Oct;5(10):e1000525
19798436
Trop Med Int Health. 2005 Dec;10(12):1321-4
16359414
Emerg Infect Dis. 2007 Feb;13(2):199-206
17479880
J Med Entomol. 2009 May;46(3):505-10
19496420
Science. 2005 Jun 10;308(5728):1638-41
15947189
PLoS Biol. 2009 Apr 7;7(4):e1000058
19355786
Science. 2005 Jun 10;308(5728):1641-2
15947190
Science. 2009 Jan 2;323(5910):51-2
19119208
Malar J. 2010 Jun 16;9:168
20553597
Trends Ecol Evol. 2005 Nov;20(11):577-9
16701437