| In Hainan,pig farms are mostly located in remote mountains,forests and villages,and their unique surrounding environment and abundant sources of blood meels facilitate mosquito breeding.Mosquito bites not only cause restlessness and skin diseases in pigs,which affect the pig growth rate and the productivity of pig farms,but also spread a variety of mosquito-borne diseases,posing a great threat to the health of both pig farm workers and pigs.Understanding the population density and activity of mosquitoes in pig farms is of great significance to the prevention and control of mosquitoes in pig farms.We therefore carried out the following studies:1.Morphological and molecular identification and COI sequence analysis of major mosquito species in pig farms.In this experiment,the mosquitoes of pig farms were morphologically identified under a microscope.We found five main mosquito species belonging to 5 genera,namely Culex tritaeniorhynchus,Armigeres subalbatus,Mansonia uniformis,Aedes albopictus and Anopheles sinensis.In addition,Aedes vexans was also caught in a breeder pig farm in Tunchang county.The DNA of mosquito was extracted,a fragment of COI gene sequence was amplified,and then sequenced.After sequence comparison,it was found that there were some mistakes in morphological identification.The species of some samples identified as Anopheles sinensis was actually Anopheles tessellatus.The genetic distances of six species of mosquitoes found in traditional pig farms were calculated,and the genetic distances of different populations were between 0.097 and 0.160.2.Investigation of mosquito population composition,density and activity pattern on pig farm.In this study,the ultraviolet lamp trap,animal net trap and pig trap were used to investigate the mosquito population composition,density and activity patterns.The results showed that the average annual mosquito densities were 4.79±4.32,15.31±16.51 and15.16±11.20 mosquitoes /(trap · h)in the pig house in family yard,traditional pig farms and intensive pig farms,respectively.The dominant species was Cx.tritaeniorhynchus,with the proportion of 70.33%,89.64% and 93.95% in the pig house in family yard,traditional pig farms and intensive pig farms,respectively.The difference in mosquito species composition ratio in all pig farms was extremely significant(P<0.001).The fluctuation patterns of mosquitoes in three different pig farms were single peak,wave and double peaks curves,and the peaks of mosquito activity appeared in October,November,July and September.The average landing index of mosquitoes in traditional pig farms was154.50±30.71 mosquitoes /(pig · h).This study showed that the three pig farms with different raising patterns all had high mosquito population density,and there was a potential risk of mosquito-borne diseases transmission.3.The treatment of spinosad microemulsion and ivermectin injection on mosquitoes in pig farms.This experiment investigated the effects of self-made spinosad microemulsion and ivermectin injection on dominant mosquito species in pig farms.Pigs were divided into three treatment groups with 3 pigs in each group.The first group was injected with self-made spinosad microemulsion at 5mg/kg body weight,the second group was injected with long-acting ivermectin injection at 0.3mg/kg body weight,and the third group was the blank control group.Mosquitoes were collected by net on the 1st,9th and 18 th day after treatment,and the dominant species were confirmed.The oviposition rate and hatching rate of the collected mosquitoes were calculated after they laid eggs.The results showed that a total of 254 mosquitoes were captured by hand-held mosquito traps during the experiment,of which Cx.tritaeniorhynchus was the dominant mosquito,accounting for 62.2%.The oviposition rates between the ivermectin group and the control group were significantly different on the first day after treatment(P<0.05).On days 1,9 and 18 after treatment,there was no significant difference between the spinosad group and the ivermectin group(P>0.05);an extremely significant difference(P< 0.01)between the spinosad group and the control group;an extremely significant difference(P<0.01)between the control group and the ivermectin group in the hatching rate.It was concluded that spinosad microemulsion preparation and ivermectin could effectively lower the hatching rate of Cx.Tritaeniorhynchus eggs,reduce the mosquito density and may improve the production efficiency of pig farms.4.The effect of mosquito bites on pigs’ weight gain,food consumption and skin health.In this experiment,mosquito nets and spraying mosquito repellents were used to create a mosquito-free or mosquito-less feeding environment.The effects of mosquito bites on pigs’ weight gain and skin health were studied by measuring pig weight gain and skin rashes.The results showed that although mosquito bites had no significant effect on pig weight gain and feed consumption,the weight gain of the mosquito-free group was greater than that of the mosquito-containing group,and the feed conversion rate was also higher than that of the mosquito-containing group;In addition,there was a significant difference in skin rashes between the mosquito-free group and the mosquito-containing group.Therefore,mosquito bites may have a certain impact on pig production speed and skin health,and farmers need to pay attention to mosquito prevention and control on pig farms. |
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