{"id":7718,"date":"2020-09-28T09:16:42","date_gmt":"2020-09-28T13:16:42","guid":{"rendered":"https:\/\/cals.ncsu.edu\/applied-ecology-new\/?p=7718"},"modified":"2020-09-28T09:16:42","modified_gmt":"2020-09-28T13:16:42","slug":"bees-can-limit-low-level-parasite-spread-within-colonies","status":"publish","type":"post","link":"https:\/\/cals.ncsu.edu\/applied-ecology\/news\/bees-can-limit-low-level-parasite-spread-within-colonies\/","title":{"rendered":"Bees Can Limit Low-Level Parasite Spread Within Colonies"},"content":{"rendered":"

When parasite pressure is low, bees can control how quickly the parasites spread within colonies, and this might be due to social immunity.<\/span><\/p>\n

All bees risk encountering parasites any time they stop at a flower. An unrelated study in New York found that as many as 1 in 10 flowers had parasites on them and flowers can be visited a few to dozens of times per day. Some flowers are more likely to harbor parasites because of their shape and the way bees move across the flower to forage. Ultimately, it is a matter of time before a bee encounters parasites and brings them back to their colony, but little was known about how parasite infections spread within colonies.<\/span><\/p>\n

A collaborative study at NC State\u2019s Department of Applied Ecology<\/a> used two agriculturally significant bee species for this study, western honey bees and common eastern bumble bees. Both species are important pollinators for native ecosystems and agricultural industries and both species have relatively large colonies, hypothetically the perfect breeding grounds for parasites.<\/span><\/p>\n

\u201cHaving healthy populations of both managed and wild bees is essential to maintain good yield of many crops,\u201d says Simon Pinilla-Gallego<\/a>, lead researcher and Ph.D. student. \u201cUnderstanding how parasites spread and what factors control their transmission dynamics are the first steps toward developing strategies to control them.\u201d<\/span><\/p>\n

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Bee size is estimated by measuring the \u201cradial cell\u201d of the wings. Researchers scan the wings and then measure them on the computer. Picture by Simon Pinilla-Gallego.<\/figcaption><\/figure>\n

For this study, colonies of both honey and bumble bees were brought to a laboratory and infected with either high or low levels of two common gut parasites, a Trypanosomatid <\/span>Crithidia bombi <\/span><\/i>that infects bumble bees and a microsporidian <\/span>Nosema ceranae <\/span><\/i>that infects honey bees. Researchers then measured the transmission rates, the severity of parasite loads in individuals, and the performance of the colonies over five to seven weeks.\u00a0<\/span><\/p>\n

In the high infection rate trials, bumble bee colonies experienced a higher spread rate of infection whereas honey bees didn\u2019t see as large of a spread as the bumble bee colonies, but the honey bees that were infected were severely infected. In the low infection rate trials, both bumble bees and honey bees were able to slow the spread of the parasites.\u00a0 This suggests that both bees are able to effectively use a secret weapon to keep low-grade infections in check, perhaps social immunity.<\/span><\/p>\n

\u201cWhen the parasite pressure is low, we suspect that the social immunity of both bee species can control the spread of the parasites in the colony, but there is a limit to that mechanism,\u201d says Pinilla-Gallego. \u201cIf the parasite pressure is too high, then the parasites will spread in the colony pretty fast, which also contributes to having more bees spreading the parasites in the environment.\u201d<\/span><\/p>\n

The more we understand about parasite transmission within bee colonies, the better farmers and ecologists can prepare for the implications of potential infections in hives.\u00a0 It also shows that taking steps to actively reduce the levels and amounts of parasites in the environment would be greatly beneficial to all pollinators.\u00a0<\/span><\/p>\n

Watch how Simon and his team conducted these experiments in Simon’s video below:<\/p>\n

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