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Zooprophylaxis or zoopotentiation: the outcome of introducing animals on vector transmission is highly dependent on the mosquito mortality while searching.

Saul A - Malar. J. (2003)

Bottom Line: Changing the accessibility of the humans had a much greater effect.Estimates of searching-associated vector mortality are essential before the effects of changing animal husbandry practices can be predicted.With realistic values of searching-associated vector mortality rates, zooprophylaxis may be ineffective.

View Article: PubMed Central - HTML - PubMed

Affiliation: Malaria Vaccine Development Unit, NIAID, NIH, Rockville, MD 20852, USA. ASaul@niaid.nih.gov

ABSTRACT

Background: Zooprophylaxis, the diversion of disease carrying insects from humans to animals, may reduce transmission of diseases such as malaria. However, as the number of animals increases, improved availability of blood meals may increase mosquito survival, thereby countering the impact of diverting feeds.

Methods: Computer simulation was used to examine the effects of animals on the transmission of human diseases by mosquitoes. Three scenarios were modelled: (1) endemic transmission, where the animals cannot be infected, eg. malaria; (2) epidemic transmission, where the animals cannot be infected but humans remain susceptible, e.g. malaria; (3) epidemic disease, where both humans and animals can be infected, but develop sterile immunity, eg. Japanese encephalitis B. For each, the passive impact of animals as well as the use of animals as bait to attract mosquitoes to insecticide was examined. The computer programmes are available from the author. A teaching model accompanies this article.

Results: For endemic and epidemic malaria with significant searching-associated vector mortality, changing animal numbers and accessibility had little impact. Changing the accessibility of the humans had a much greater effect. For diseases with an animal amplification cycle, the most critical factor was the proximity of the animals to the mosquito breeding sites.

Conclusion: Estimates of searching-associated vector mortality are essential before the effects of changing animal husbandry practices can be predicted. With realistic values of searching-associated vector mortality rates, zooprophylaxis may be ineffective. However, use of animals as bait to attract mosquitoes to insecticide is predicted to be a promising strategy.

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Simulation of an arbovirus epidemic: effect of altering the accessibility of both humans and animals. Ratio of animals to humans 1: 4 used for each curve (25 animals and 100 humans). Black line: Aa = 0.002 h-1, Ah = 0.0005 h-1 (ie. both 0.5 times as accessible as the standard conditions); red line: Aa = 0.004 h-1, Ah = 0.001 h-1 (standard conditions); green line: Aa = 0.008 h-1, Ah = 0.002 h-1 (ie. both 2 times as accessible as the standard conditions). Other parameters were those used in Fig. 6 (Table 3).
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Figure 8: Simulation of an arbovirus epidemic: effect of altering the accessibility of both humans and animals. Ratio of animals to humans 1: 4 used for each curve (25 animals and 100 humans). Black line: Aa = 0.002 h-1, Ah = 0.0005 h-1 (ie. both 0.5 times as accessible as the standard conditions); red line: Aa = 0.004 h-1, Ah = 0.001 h-1 (standard conditions); green line: Aa = 0.008 h-1, Ah = 0.002 h-1 (ie. both 2 times as accessible as the standard conditions). Other parameters were those used in Fig. 6 (Table 3).

Mentions: As for the malaria epidemic model, where there is some feeding associated vector mortality, then decreasing the accessibility of both animals and humans had a major impact on the rate at which an epidemic spread (Fig. 8).


Zooprophylaxis or zoopotentiation: the outcome of introducing animals on vector transmission is highly dependent on the mosquito mortality while searching.

Saul A - Malar. J. (2003)

Simulation of an arbovirus epidemic: effect of altering the accessibility of both humans and animals. Ratio of animals to humans 1: 4 used for each curve (25 animals and 100 humans). Black line: Aa = 0.002 h-1, Ah = 0.0005 h-1 (ie. both 0.5 times as accessible as the standard conditions); red line: Aa = 0.004 h-1, Ah = 0.001 h-1 (standard conditions); green line: Aa = 0.008 h-1, Ah = 0.002 h-1 (ie. both 2 times as accessible as the standard conditions). Other parameters were those used in Fig. 6 (Table 3).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC222927&req=5

Figure 8: Simulation of an arbovirus epidemic: effect of altering the accessibility of both humans and animals. Ratio of animals to humans 1: 4 used for each curve (25 animals and 100 humans). Black line: Aa = 0.002 h-1, Ah = 0.0005 h-1 (ie. both 0.5 times as accessible as the standard conditions); red line: Aa = 0.004 h-1, Ah = 0.001 h-1 (standard conditions); green line: Aa = 0.008 h-1, Ah = 0.002 h-1 (ie. both 2 times as accessible as the standard conditions). Other parameters were those used in Fig. 6 (Table 3).
Mentions: As for the malaria epidemic model, where there is some feeding associated vector mortality, then decreasing the accessibility of both animals and humans had a major impact on the rate at which an epidemic spread (Fig. 8).

Bottom Line: Changing the accessibility of the humans had a much greater effect.Estimates of searching-associated vector mortality are essential before the effects of changing animal husbandry practices can be predicted.With realistic values of searching-associated vector mortality rates, zooprophylaxis may be ineffective.

View Article: PubMed Central - HTML - PubMed

Affiliation: Malaria Vaccine Development Unit, NIAID, NIH, Rockville, MD 20852, USA. ASaul@niaid.nih.gov

ABSTRACT

Background: Zooprophylaxis, the diversion of disease carrying insects from humans to animals, may reduce transmission of diseases such as malaria. However, as the number of animals increases, improved availability of blood meals may increase mosquito survival, thereby countering the impact of diverting feeds.

Methods: Computer simulation was used to examine the effects of animals on the transmission of human diseases by mosquitoes. Three scenarios were modelled: (1) endemic transmission, where the animals cannot be infected, eg. malaria; (2) epidemic transmission, where the animals cannot be infected but humans remain susceptible, e.g. malaria; (3) epidemic disease, where both humans and animals can be infected, but develop sterile immunity, eg. Japanese encephalitis B. For each, the passive impact of animals as well as the use of animals as bait to attract mosquitoes to insecticide was examined. The computer programmes are available from the author. A teaching model accompanies this article.

Results: For endemic and epidemic malaria with significant searching-associated vector mortality, changing animal numbers and accessibility had little impact. Changing the accessibility of the humans had a much greater effect. For diseases with an animal amplification cycle, the most critical factor was the proximity of the animals to the mosquito breeding sites.

Conclusion: Estimates of searching-associated vector mortality are essential before the effects of changing animal husbandry practices can be predicted. With realistic values of searching-associated vector mortality rates, zooprophylaxis may be ineffective. However, use of animals as bait to attract mosquitoes to insecticide is predicted to be a promising strategy.

Show MeSH
Related in: MedlinePlus