Volume 17, Number 7—July 2011
Research
Co-infections of Plasmodium knowlesi, P. falciparum, and P. vivax among Humans and Anopheles dirus Mosquitoes, Southern Vietnam
, Richard Culleton, Yoshimasa Maeno, Nguyen Tuyen Quang, and Shusuke NakazawaTable A1
Results of the collection, dissections and PCR processing of Anopheles dirus mosquitoes caught by human landing catch in the forest of Khanh Phu, Vietnam, 2009–2010
| An. dirus collections |
Midgut |
Ovaries |
Salivary glands |
PCR tested |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Date, y, mo | No. caught | No. nights | Biting density* | No. dissected | No. oocysts. | No. parous | No. not parous. | No. dissected | No. sporozoites. | EIR† | No. PCR | No. P.k‡ |
| 2008 | ||||||||||||
| Jan | 194 | 35 | 5.5 | 146 | 1 | 161 | 33 | 194 | 6 | 0.17 | 2 | – |
| Feb | 47 | 26 | 1.8 | 27 | – | 42 | 5 | 47 | – | 0.00 | – | – |
| Mar | 87 | 60 | 1.5 | 41 | 1 | 58 | 27 | 87 | 4 | 0.07 | – | – |
| Apr | 107 | 60 | 1.8 | 45 | 1 | 74 | 33 | 107 | 2 | 0.03 | 2 | – |
| May | 39 | 59 | 0.7 | 21 | – | 30 | 9 | 39 | – | 0.00 | – | – |
| Jun | 71 | 60 | 1.2 | 42 | – | 54 | 17 | 71 | 1 | 0.02 | 1 | – |
| Jul | 28 | 60 | 0.5 | 16 | – | 24 | 4 | 28 | – | 0.00 | – | – |
| Aug | 20 | 58 | 0.3 | 7 | – | 17 | 3 | 20 | 1 | 0.02 | 1 | 1§ |
| Sep | 135 | 57 | 2.4 | 56 | – | 98 | 36 | 134 | – | 0.00 | – | – |
| Oct | 567 | 59 | 9.6 | 293 | 1 | 456 | 111 | 567 | 2 | 0.03 | – | – |
| Nov | 607 | 59 | 10.3 | 335 | 1 | 428 | 179 | 607 | 5 | 0.08 | 3 | |
| Dec | 203 | 60 | 3.4 | 116 | 2 | 156 | 47 | 203 | 1 | 0.02 | 1 | 1 |
| 2009 | ||||||||||||
| Jan | 88 | 32 | 2.8 | 39 | – | 79 | 9 | 88 | 1 | 0.03 | 1 | 1 |
| Feb | 387 | 40 | 9.7 | 198 | 2 | 307 | 78 | 385 | 5 | 0.13 | 4 | 2 |
| Mar | 499 | 50 | 10.0 | 282 | 1 | 380 | 119 | 499 | 6 | 0.12 | 6 | 3 |
| Apr | 193 | 50 | 3.9 | 106 | 2 | 149 | 44 | 193 | 4 | 0.08 | 4 | 2 |
| May | 81 | 47 | 1.7 | 35 | – | 70 | 11 | 81 | 4 | 0.09 | 4 | 3 |
| Jun | 85 | 50 | 1.7 | 37 | – | 63 | 22 | 85 | 3 | 0.06 | 3 | 1 |
| Jul | 65 | 49 | 1.3 | 45 | 2 | 56 | 8 | 64 | 3 | 0.06 | 3 | 2 |
| Aug | 178 | 49 | 3.6 | 89 | – | 142 | 36 | 178 | 1 | 0.02 | 1 | – |
| Sep | 220 | 50 | 4.4 | 131 | – | 158 | 50 | 208 | 0.00 | – | – | |
| Oct | 364 | 50 | 7.3 | 209 | 1 | 272 | 93 | 365 | 2 | 0.04 | 2 | 1 |
| Nov | 278 | 50 | 5.6 | 175 | – | 184 | 100 | 284 | 1 | 0.02 | 1 | – |
| Dec | 380 | 50 | 7.6 | 215 | 4 | 290 | 81 | 371 | 2 | 0.04 | 2 | – |
| 2010 | ||||||||||||
| Jan | 559 | 49 | 11.4 | 345 | 9 | 453 | 108 | 561 | 29 | 0.59 | 29 | 13 |
| Feb |
222 |
16 |
13.9 |
132 |
2 |
153 |
44 |
197 |
6 |
0.42 |
3 |
1 |
| Totals over 26 mo | 5,704 | 1,285 | 4.44 | 3,183 | 30 | 4,354 | 1,307 | 5,663 | 89 | 0.07 | 73 | 31 |
| Averages: | % oocysts | % parous | % sporozoites | Annual EIR¶ | % P.k positive# | |||||||
| 0.94 | 76.9 | 1.57 | 25.46 | 42 | ||||||||
**Biting density = monthly average no. of bites by An. dirus/person-night; –, not found.
†EIR, entomologic inoculation rate expressed as the monthly average no. of sporozoite-infected bites/person-night.
‡P.k, no. of mosquito salivary glands that were positive for Plasmodium knowlesi.
§The analysis of the first mosquito found with P. knowlesi in August 2008 was described in Nakazawa et al. (11).
¶Annual EIR calculated from the average 0.07 infective bites/person-night over the whole period of 26 mo, then multiplied by 365.
#The percentage of P. knowlesi–positive salivary glands among the sporozoite-positive salivary glands that underwent PCR.
