| xmrv | 21 | no rank | viruses | viruses | 438045 |
| wongorr virus | 1 | species | viruses | viruses | 47465 |
| wenyonella gagari | -3 | species | | protozoa | |
| wenyonella anatis | -3 | species | | protozoa | |
| wehrdikmansia wenki | -3 | species | | helminths | |
| wehrdikmansia rugosicauda | 2 | species | | helminths | |
| wehrdikmansia flexuosa | -3 | species | | helminths | |
| wehrdikmansia cervipedis | 1 | species | | helminths | |
| warrego virus | 2 | species | viruses | viruses | 40062 |
| wallal virus | 3 | species | viruses | viruses | 40061 |
| vogesella indigofera | 15 | species | bacteria | bacteria | 45465 |
| vogeloides massinoi | -3 | species | | helminths | |
| varestrongylus pneumonicus | 1 | species | | helminths | |
| uncinaria lucasi | 8 | species | | helminths | 1080936 |
| uncinaria criniformis | 3 | species | | helminths | |
| tyzzeria pellerdyi | -3 | species | | protozoa | |
| tyzzeria alleni | -3 | species | | protozoa | |
| trypanosoma uniforme | 1 | species | | protozoa | |
| trypanosoma saimirii | 2 | species | | protozoa | |
| trypanosoma rabinowitschae | -3 | species | invertebrates | protozoa | 267967 |
| trypanosoma primatum | -3 | species | | protozoa | |
| trypanosoma minasense | 5 | species | invertebrates | protozoa | 83893 |
| trypanosoma duttoni | 9 | species | | protozoa | |
| trypanosoma dimorphon | 2 | species | | protozoa | |
| trypanosoma diasi | -3 | species | | protozoa | |
| troglostrongylus subcrenatus | -3 | species | | helminths | |
| triodontophorus serratus | 5 | species | invertebrates | helminths | 54002 |
| triodontophorus minor | -3 | species | | helminths | 1735159 |
| triodontophorus brevicauda | -3 | species | invertebrates | helminths | 1628841 |
| trinoton anserinum | 3 | species | | | |
| trimenopon hispidum | 1 | species | | | |
| trichuris tenuis | 5 | species | | helminths | |
| trichuris sylvilagi | 1 | species | | helminths | |
| trichuris skrjabini | 4 | species | invertebrates | helminths | 198341 |
| trichuris serrata | 1 | species | | helminths | 1610522 |
| trichuris raoi | -3 | species | | helminths | |
| trichuris leporis | 6 | species | invertebrates | helminths | 109045 |
| trichuris campanula | 2 | species | | helminths | |
| trichuris cameli | -3 | species | | helminths | |
| trichomonas macacovaginae | -3 | species | | protozoa | |
| trichomonas caballi | -3 | species | | protozoa | |
| trichomitus wenyoni | -3 | species | | protozoa | |
| trichomitus fecalis | -3 | species | | protozoa | |
| trichodectes sphaerocephalus | -3 | species | | | |
| trichodectes scalaris | -3 | species | | | |
| trichodectes parumpilosus | -3 | species | | | |
| trichodectes limbatus | -3 | species | | | |
| trichodectes climax | -3 | species | | | |
| trichodectes canis | 4 | species | invertebrates | | 209909 |
| treponema vincentii | 19 | species | bacteria | bacteria | 69710 |
| treponema putidum | 3 | species | bacteria | bacteria | 221027 |
| toxocara malaysiensis | 4 | species | invertebrates | helminths | 321166 |
| torque teno midi virus | 4 | species | viruses | viruses | 432261 |
| thelohania baueri | -3 | species | | fungi | |
| thelohania apodemi | 3 | species | | fungi | |
| theileria tarandi | -3 | species | | protozoa | |
| theileria | 63 | genus | invertebrates | | 5873 |
| tetratrichomonas pavlovi | -3 | species | | protozoa | |
| tetratrichomonas microti | -3 | species | | protozoa | |
| tetrameres mohtedai | 2 | species | | helminths | |
| tetrameres fissipina | -3 | species | invertebrates | helminths | 435743 |
| tetrameres crami | -3 | species | | helminths | |
| tetrameres confusa | 1 | species | | helminths | |
| tetrameres americana | 6 | species | | helminths | |
| tetnovirus 1 | 1 | species | viruses | viruses | 870711 |
| tembusu virus | 1 | species | viruses | viruses | 64293 |
| taenia saginata asiatica | 6 | subspecies | invertebrates | helminths | 246341 |
| taenia martis | 3 | species | invertebrates | helminths | 159981 |
| taenia crassiceps | 36 | species | invertebrates | helminths | 6207 |
| taenia (multiceps) longihamatus | -3 | species | | helminths | |
| taenia (multiceps) glomratus | -3 | species | | helminths | |
| stellantchasmus amplicaecalis | -3 | species | | helminths | |
| spirura talpae | 2 | species | | helminths | |
| spirura rytipleurites seurati | 2 | subspecies | | helminths | |
| spirura rytipleurites rytiplanites | -3 | subspecies | | helminths | |
| spirura rytipleurites | 2 | species | | helminths | |
| spirura | 4 | genus | | | |
| spiculopteragia spiculoptera | 5 | species | invertebrates | helminths | 126399 |
| spiculopteragia peruviana | -3 | species | | helminths | |
| spiculopteragia boehmi | 3 | species | invertebrates | helminths | 239091 |
| spiculocaulus orloffi | -3 | species | | helminths | |
| spiculocaulus leuckarti | -3 | species | | helminths | 1418103 |
| spiculocaulus kwongi | -3 | species | | helminths | |
| spiculocaulus austriacus | -3 | species | | helminths | |
| soboliphyme baturini | 4 | species | invertebrates | helminths | 241478 |
| small anellovirus | 5 | species | viruses | viruses | 393049 |
| skrjabinagylus petrowi | -3 | species | | helminths | |
| skrjabinagylus nasicola | -3 | species | | helminths | |
| skrjabinagylus magnus | -3 | species | | helminths | |
| skrjabinagylus chitwoodorum | -3 | species | | helminths | |
| skrjabinagylus | -3 | genus | | | |
| skrjabinagia kolchida | 2 | species | | helminths | |
| skrjabinagia dagestanica | -3 | species | | helminths | |
| skrjabinagia boevi | 1 | species | | helminths | |
| simondsia paradoxa | 2 | species | | helminths | |
| simondsia | 3 | genus | | | |
| sarcocystis tarandi | 2 | species | invertebrates | protozoa | 425663 |
| sarcocystis sinensis | 1 | species | invertebrates | protozoa | 103879 |
| sarcocystis rangiferi | 3 | species | invertebrates | protozoa | 425662 |
| sarcocystis ovalis | 2 | species | invertebrates | protozoa | 501322 |