ticks have coevolved with various wild animal hosts which are reservoir hosts for pathogens such as fungi , bacteria , viruses , rickettsiae , and protozoan which can be transmitted to domestic mammals and humans [ 13 ] . ticks that feed on feral or domestic pigs ( sus scrofa ) and their tick - borne diseases have been previously studied worldwide [ 47 ] . the most common tick species reported in association with domestic pigs in brazil is amblyomma cajennense ( fabricius , 1787 ) , an eclectic tick that has a broad range of hosts and widespread distribution [ 810 ] . in brazil a second genus reported in association with brazilian pigs is the genus ornithodoros , which has two species : o. rostratus and o. brasiliensis . both of these species have also been reported in association with wild native pigs ( tayassu sp . ) the pantanal ecosystem is considered to be one of the most well - preserved biomes in brazil and was added to the unesco world heritage list in 2000 . the brazilian pantanal has been described as a  biological hotspot  for conservation and one of the richest and the most diverse ecosystems in the world . in this biome , wild animals and their parasites engage in complex and dynamic interactions . however , this environment has been modified in the last two decades due to a large substitution of forested areas by exotic pasture to increase the livestock population . domestic pigs ( sus scrofa ) were introduced to the pantanal by european settlers around two hundred years ago . some escaped and became wild , giving rise to the current feral pig population [ 13 , 14 ] . this foreign species is considered one of the  world 's worst invasive alien species  by the world conservation union . the population of feral pigs is expanding and its complete elimination from the pantanal is now considered impossible . the population is currently estimated at over one million animals , dispersed in 10,000 groups . the ecoepidemiological impact caused by feral pigs and their associated parasites in the pantanal wetlands is unknown . feral pigs are the main hunting target and are effectively acting as a replacement species for the hunting of native wildlife in the pantanal . furthermore , since the feral pig is the main species hunted by local people , close contact with pigs during this traditional hunting practice may increase disease transmission to humans . the brazilian pantanal is an important area for conservation purposes and the cattle ranching industry in latin america . in spite of this importance to the brazilian economy , the ecology of ticks and tick - borne pathogens that infect free - living mammals in this region is poorly known . the aim of the present study was to describe tick fauna from feral pigs in nhecolndia , a subregion of the brazilian pantanal , and to seek information about , tick biology , sex ratio , and seasonality . the nhecolndia sub - region has a tropical climate with weather conditions that are markedly seasonal . the wet season ( november  april ) is hot and humid while the dry season ( may  october ) is warm . during the wet season , many parts of open grassland change from terrestrial to aquatic habitats . in the dry season , the land dries out and only scarce pools , creeks , and some lakes remain . ( savanna ) , patches of forest , grasslands , and shallow lake basins . the feral pigs were captured alive with the help of local people in two different seasons . the first capture trip was in the dry season , between july and october of 2004 , when 21 feral pigs were captured . the second trip was in the wet season , in january of 2005 , when 23 feral pigs were captured . the pigs were captured by fence traps or by cowboys who used a lasso to catch them . all captured pigs were tranquilized ( tiletamine and zolazepam  zoletil ) prior to examination and tick collection . all trapping and handling procedures were conducted in accordance with the authorization of the brazilian environment institute ( ibama ) ( license no . all of the ticks collected from each animal were placed into plastic flasks with 70% ethanol . during the second trip , engorged females were maintained in small plastic boxes with a humid hydrophilic cotton ball to allow oviposition and larval eclosion . generally , these two life cycle parameters are good predictors of host adequacy in tick biology . ticks were identified using published morphological keys for neotropical ticks [ 2022 ] and by comparison with specimens housed in the tick collection of the instituto butantan ( sp , brazil ) , under the care of curator dr . quantitative descriptors ( prevalence and mean abundance ) were calculated for each parasite species , with males and females recorded separately . possible differences between prevalence ( number of parasitized feral pigs in a given group of captured feral pigs ) and mean abundance ( mean quantity of ticks collected from each feral pig ) were tested for the two different seasons using fisher 's exact test ( prevalence ) and student 's t - test ( mean abundance ) , with previously log(x + 1 ) transformed intensity of infestation data . the ratio of the variance to the mean abundance ( di ) and the index of discrepancy ( d ) were used to determine distribution patterns . discriminant analysis , based on the mahalanobis distance , was used to find differences between the two seasons , to classify different groups of hosts and to identify which parasite species were responsible for these differences . three tick species were found to be feeding on feral pigs in the nhecolndia region : amblyomma cajennense , a. parvum , and ornithodoros rostratus . in both seasons , only adult amblyomma were found . during the dry season , a total of 178 specimens of a. cajennese ( 8.48  4.36 ticks / host59 female and 119 male specimens ) and 12 specimens of a. parvum ( 0.57  1.78 ticks / host  four female and eight male specimens ) were collected . in the wet season , a total of 127 specimens of a. cajennense were collected ( 5.52  3.2 ticks / host49 female and 78 male specimens ) , as well as four females of a. parvum ( 0.17  0.49 ticks / host ) ( table 1 ) . a sex ratio of 1  :  0.50 and 1  :  0.63 ( males  :  females ) was found for a. cajennense in the dry and wet seasons , respectively . the values of prevalence , mean abundance , and mean intensity of infestations and their possible differences can be seen in table 2 . the ticks did not exhibit a preference for any region of the pig 's body and were collected from the rostrum , head , ears , neck , thorax , back , and members . all a. cajennense ( 23 ) or a. parvum ( 5 ) engorged females laid eggs with good hatch ( > 90% ) . dimensionality tests for group separation revealed two distinct host groups (  = 11.31 ;  p = 0.02 ) . a significant overall effect was observed ( wilk 's lambda = 0.75 ; f4,39 , p = 0.02 ) . each host specimen was 70.3% well classified in the two distinct groups ( table 4 ) . the difference of prevalence and intensity for a. cajennense male infestation between the seasons was the most significant ( 95.7% ) in determining the position of hosts among the groups ( figure 1 ) . o. rostratus was only collected on one occasion ( 4 nymphs ) during the wet season , feeding on the belly region ( figure 2(c ) ) . three nymphs molted to adults ( two females and one male ) in the laboratory . the ecchymosis - like lesions observed in experimentally infested domestic pigs were similar to those found in naturally infested feral pigs . although o. rostratus was not found , similar lesions were observed on domestic dogs and humans in the studied area ( figures 2(a ) , 2(b ) and 2(c ) ) . the prevalence and intensity of a. cajennense infestation found to be feeding on feral pigs , based on the observation that all engorged females laid viable eggs with a good hatching percentage ( > 90% ) , strongly suggest that this introduced mammal species is a very adequate host for this hard tick in the southern pantanal region . considering that feral pigs represent one of the major biomass free - living mammals in the studied area , as well as the fact that a. cajennense is a multi - host parasite , its amplification through feral pigs may play an important role in the health conditions of local wildlife , domestic animals , and people . in fact , a number of mammal species commonly found in the southern pantanal have previously been naturally infested by a. cajennense : the collared peccary ( pecari tajacu ) ; the white - lipped peccary ( tayassu pecari ) ; the giant anteater ( myrmecophaga tridactyla ) ; the collared anteater ( tamandua tetradactyla ) ; the coati ( nasua nasua ) ; the capybara ( hydrochaeris hydrochaeris ) ; the marsh deer ( blastocerus dichotomus ) ; and the brown brocket deer ( mazama gouazoubira ) [ 2830 ] . the crab - eating fox ( cerdocyon thous ) , the ocelot ( leopardus pardalis ) , and certain small rodents are examples of other wild mammals that have been infested by a. cajennense in the same studied area ( ongoing unpublished research ) . this situation is a very good example of man - made opportunities for neo - tropical tick development . the same author describes the expansion of the cayenne tick 's ( a. cajennense ) geographical range as a result of its association with feral pigs , which are a highly mobile host . the discriminant analysis confirmed that a. cajennense was more abundant in the nhecolndia sub - region during the dry season . in total , 70% of the feral pigs examined were correctly classified according to the seasons , considering the distribution of male a. cajennense to be responsible for this difference . these results are not in accordance with previously published studies . according to a number of studies , adult a. cajennense are more prevalent during the wet season [ 29 , 3136 ] because the annual water cycle in the pantanal region is unique and differs from other brazilian regions . since this research comprises only one dry or wet season , more research concerning a. cajennense seasonality should be conducted before any solid conclusion . the higher intensity of infestation of male a. cajennense in relation to females in naturally infested feral pigs was probably due to the longer parasitic period of males . the results of the present study also suggest that feral pigs seem to be a good host for a. parvum in the southern pantanal because ( a ) the prevalence was 15% and ( b ) all engorged females that were collected from feral pigs laid viable eggs from which hatched larvae were used to start a laboratory colony . considering the constant environmental modifications by human activities in the pantanal region and the broad host range of a. parvum , which has been reported to be infesting cattle , wild carnivores , giant anteaters , and deer [ 29 , 30 , 37 , 38 ] , feral pigs might be also an important source of infestation in domestic animals and humans . the recent discovery of a novel spotted fever group , rickettsia sp . , in a. parvum ticks from argentina   is a concern in the studied area .   with regard to infestations by o. rostratus these partial results indicate that feral pigs can be a source of infestation for domestic animals in the region studied . people who have been bitten reported fever , swollen lymph nodes , and an intensive itch . the role of o. rostratus as a vector of tick - borne pathogens is poorly understood , although this tick is considered to be a vector of spotted fever [ 40 , 41 ] . the three tick species found in the present study , a. cajennense , a. parvum , and o. rostratus , are able to cross - infect wildlife , domestic animals , and humans . this hosts ' multiplicity suggests the existence of a complex network in the eco - epidemiology of these ticks in the pantanal region . finally , one of the main causes of disease emergence or reemergence is environmental alterations that increase the contact between wildlife and domestic animals and its consequent modification of epidemiological profiles . these feral pigs are an alien species which became greatly abundant and share the same habitat as autochthone wildlife and livestock . the role of their associated tick species in disease epidemiology needs to be widely investigated as a major concern for cattle production and wildlife conservation . in conclusion , ticks related to feral pigs may become a significant problem for humans , wildlife , and the health of livestock in the pantanal region .
feral pigs ( s. scrofa ) were introduced to the pantanal region around 200 years ago and the population appears to be in expansion . its eradication is considered to be impossible . the population of feral pigs in the pantanal wetlands is currently estimated at one million . 
 two scientific excursions were organized . 
 the first was conducted during the dry season , when 21 feral pigs were captured and the second was during the wet season , when 23 feral pigs were captured . 
 ticks were collected and the oviposition and hatching process were studied to confirm the biological success of each tick species . 
 three tick species were found to be feeding on feral pigs : amblyomma cajennense , a. parvum , and ornithodoros rostratus . during the dry season , 
 178 adult a. cajennense were collected , contrasting with 127 a. cajennense specimens in the wet season . 
 this suggests that the seasonality of these ticks in the brazilian pantanal wetlands could be different from other regions . 
 the results indicate that a. parvum and a. cajennense are biologically successful parasites in relation to feral pigs . 
 a. cajennense appears to have adapted to this tick - host relationship , as well as the areas where feral pigs are abundant , and could play a role in the amplification of this tick population .