| mesogyna hepatica | 1 | species | | helminths | |
| metathelazia | 3 | genus | | | |
| metathelazia californica | 1 | species | | helminths | |
| metathelazia felis | -3 | species | | helminths | |
| metathelazia multipapillata | -3 | species | | helminths | |
| microthoracius cameli | -3 | species | | | |
| microthoracius mazzai | 2 | species | | | |
| microthoracius minor | -3 | species | | | |
| microthoracius praelongiceps | -3 | species | | | |
| mlv-related virus cfs | -3 | no rank | viruses | viruses | 878322 |
| morellia aenescens | -3 | species | invertebrates | fly | 559657 |
| morellia hortorum | -3 | species | invertebrates | fly | 559658 |
| morellia simplex | -3 | species | invertebrates | fly | 559659 |
| mosgovoyia pectinata | 4 | species | invertebrates | helminths | 160006 |
| mouse adeno-associated virus 1 | -3 | species | viruses | viruses | 341226 |
| mouse parvovirus 1 | 8 | species | viruses | viruses | 35340 |
| murshidia murshida | 1 | species | | helminths | |
| mycobacterium riyadhense | 1 | species | bacteria | bacteria | 486698 |
| mycobacterium visibile | 1 | species | bacteria | bacteria | 180224 |
| mycoplasma alkalescens | 8 | species | bacteria | bacteria | 45363 |
| mycoplasma equirhinis | 2 | species | bacteria | bacteria | 92402 |
| mycoplasma gallinarum | 6 | species | bacteria | bacteria | 29557 |
| mycoplasma mucosicanis | -3 | species | bacteria | bacteria | 458208 |
| naegleria philippinensis | -3 | species | invertebrates | protozoa | 160659 |
| necropsobacter rosorum | -3 | species | bacteria | bacteria | 908285 |
| neisseria shayeganii | 1 | species | bacteria | bacteria | 607712 |
| nematodirella cameli | 1 | species | invertebrates | helminths | 911091 |
| nematodirella dromedarii | 1 | species | | helminths | |
| nematodirella longispiculata | 1 | species | | helminths | |
| nematodiroides zembrae | 2 | species | invertebrates | helminths | 126394 |
| nematodirus europaeus | 2 | species | invertebrates | helminths | 94040 |
| nematodirus helvetianus | 16 | species | invertebrates | helminths | 61842 |
| neoctenotaenia ctenoides | 5 | species | invertebrates | helminths | 227337 |
| neocuterebra squamosa | 1 | species | | fly | |
| neospora hughesi | 13 | species | invertebrates | protozoa | 83675 |
| neostrongylus linearis | 7 | species | | helminths | |
| oesophagodontus robustus | 5 | species | invertebrates | helminths | 53340 |
| oestromyia leporina | 2 | species | invertebrates | fly | 170914 |
| okadaella gastrococcus | 1 | species | bacteria | bacteria | 948105 |
| oncicola canis | 3 | species | | helminths | |
| ophionyssus natricis | 6 | species | invertebrates | | 704026 |
| ornithofilaria fallisensis | 1 | species | | helminths | |
| ovine enzootic nasal tumor virus | 13 | species | viruses | viruses | 69576 |
| ovine mastadenovirus b | -3 | species | viruses | viruses | 389483 |
| oxyspirura mansoni | 1 | species | | helminths | |
| oxyspirura parvorum | -3 | species | | helminths | |
| parafilaroides decorus | 3 | species | invertebrates | helminths | 242456 |
| parafilaroides gymnurus | 4 | species | invertebrates | helminths | 690305 |
| parafilaroides nanus | -3 | species | | helminths | |
| parafilaroides prolificus | -3 | species | | helminths | |
| parelaphostrongylus andersoni | 9 | species | invertebrates | helminths | 192632 |
| parelaphostrongylus odocoilei | 10 | species | invertebrates | helminths | 192633 |
| paryphostomum sufratyfex | -3 | species | | helminths | |
| pasteurella tularensis | 23 | species | | bacteria | |
| pentastoma najae | -3 | species | | | |
| pharyngobolus africanus | -3 | species | | fly | |
| pigeon coronavirus | 1 | no rank | viruses | viruses | 300189 |
| placobdella rugosa | -3 | species | | | 1258696 |
| plasmodium berghei | 85 | species | invertebrates | protozoa | 5821 |
| plasmodium chabaudi | 67 | species | invertebrates | protozoa | 5825 |
| plasmodium elongatum | 13 | species | invertebrates | protozoa | 77517 |
| plasmodium fallax | 7 | species | | protozoa | |
| plasmodium hexamerium | 6 | species | | protozoa | |
| plasmodium lophurae | 34 | species | invertebrates | protozoa | 5853 |
| plasmodium rouxi | 2 | species | invertebrates | protozoa | 215558 |
| plasmodium vinckei | 33 | species | invertebrates | protozoa | 5860 |
| pneumonyssus caninum | 6 | species | | | |
| pneumospirura bassarisci | -3 | species | | helminths | |
| pneumospirura capsulata | -3 | species | | helminths | |
| pneumospirura rodentium | 1 | species | | helminths | |
| polymorphus magnus | 3 | species | | helminths | |
| polyplax serrata | 10 | species | invertebrates | | 468196 |
| polyplax spinulosa | 6 | species | invertebrates | | 468197 |
| pomphorhynchus laevis | 30 | species | invertebrates | helminths | 141832 |
| porcine picobirnavirus 1 | -3 | species | viruses | viruses | 464983 |
| porcine torovirus | 5 | species | viruses | viruses | 237020 |
| porcine type-c oncovirus | -3 | species | viruses | viruses | 369960 |
| porocephalus clavatus | 2 | species | | | |
| porocephalus subulifer | -3 | species | | | |
| poteriostomum imparidentatum | 2 | species | invertebrates | helminths | 54000 |
| poteriostomum ratzii | 1 | species | invertebrates | helminths | 53999 |
| propionibacterium acidifaciens | 1 | species | bacteria | bacteria | 556499 |
| protospirura | 9 | genus | | | 1080593 |
| protospirura bestianum | -3 | species | | helminths | |
| protospirura muricola | 7 | species | | helminths | 1766045 |
| protospirura numidia | -3 | species | | helminths | |
| protostrongylus boughtoni | 7 | species | invertebrates | helminths | 544912 |
| protostrongylus pulmonalis | 2 | species | invertebrates | helminths | 544913 |
| protostrongylus rupicaprae | 1 | species | invertebrates | helminths | 544914 |
| pseudostertagia | 1 | genus | | | |
| quilonia ethiopica | -3 | species | | helminths | |
| quilonia renniei | -3 | species | | helminths | |
| quilonia travancra | -3 | species | | helminths | |
| quilonia uganda | -3 | species | | helminths | |
| rabbit vesivirus | 2 | species | viruses | viruses | 303317 |
| raillietiella | 13 | genus | invertebrates | | 311330 |
| raillietina | 15 | genus | invertebrates | | 70662 |
| reduviidae | 43 | family | invertebrates | | 27479 |
| reighardia | 9 | genus | invertebrates | | 245000 |
| rhabditoides inermis | -3 | species | invertebrates | helminths | 96661 |