Little is known about the genetic characteristics, distribution, and transmission cycles of Cryptosporidium species that cause human disease in New Zealand. To address these questions, 423 fecal specimens containing Cryptosporidium oocysts and obtained from different regions were examined by the PCR-restriction fragment length polymorphism technique. Indeterminant results were resolved by DNA sequence analysis. Two regions supplied the majority of isolates: one rural and one urban. Overall, Cryptosporidium hominis accounted for 47% of the isolates, with the remaining 53% being the C. parvum bovine genotype. A difference, however, was observed between the Cryptosporidium species from rural and urban isolates, with C. hominis dominant in the urban region, whereas the C. parvum bovine genotype was prevalent in rural New Zealand. A shift in transmission cycles was detected between seasons, with an anthroponotic cycle in autumn and a zoonotic cycle in spring. A novel Cryptosporidium sp., which on DNA sequence analysis showed a close relationship with C. canis, was detected in two unrelated children from different regions, illustrating the genetic diversity within this genus.

Chronic non-progressive pneumonia (CNP) is a common disease which affects lambs in New Zealand during late summer and autumn. Mycoplasma ovipneumoniae can be recovered from a high proportion of lesions but it is also present in some normal lungs. Bacteria, especially Pasteurella haemolytica, can also be recovered from more than half the lungs of affected animals. Isolates of M. ovipneumoniae are genetically heterogeneous, as demonstrated by examination of their DNA or total cellular proteins, and are serologically heterogeneous as shown by metabolic inhibition tests. The number of strains present in New Zealand is large and several distinguishable strains can be recovered from each affected lung. Mycoplasma ovipneumoniae has pathogenic potential as indicated by its ability to produce hydrogen peroxide, cause ciliostasis and by its possession of a capsule. Chronic non-progressive pneumonia can be transmitted consistently to over 50% of lambs by inoculation of pooled pneumonic lung homogenate and transmission can be suppressed by broad spectrum antibiotics. In contrast, penicillin does not prevent the development of lesions but diminishes their severity. Pooled lung homogenate treated with digitonin, which inactivates mycoplasmas, has failed to transmit CNP. Pure cultures of M. ovipneumoniae produce only mild lesions in some animals, whereas inoculation with pooled lung homogenate (from which no viruses were isolated) containing mixed strains of M. ovipneumoniae and free from bacteria, is more effective in producing lesions. Research work to date suggests that CNP may be initiated by colonisation of the lung by M. ovipneumoniae which causes ciliostasis and elicits an exudate allowing colonisation of the lungs by bacteria especially M. haemolytica and by other strains of M. ovipneumoniae. The immune response to the initial strain of M. ovipneumoniae may inhibit its replication but would be less effective in inhibiting heterologous strains of the organism allowing their sequential replication. Eventually production of a broad immune response to M. ovipneumoniae would lead to its elimination which in turn would facilitate the elimination of other microorganisms and the resolution of lesions. As natural immunity to CNP occurs within the first year, it may be possible to develop an effective and useful vaccine. Such a vaccine may need to include multiple strains of M. ovipneumoniae.

Giardia intestinalis and Cryptosporidium parvum are commonly acquired waterborne parasites but little is known about their transmission cycles with regard to humans and animals. Faecal samples were collected over two time periods within the Waikato region of New Zealand from dairy cattle and humans and all positive isolates were genotyped. Of the 724 faecal specimens examined (354 cows, 304 calves and 66 humans), 16 cows, 32 calves and 5 humans were positive for G. intestinalis. Phylogenetic group 1 was found in 26 G. intestinalis positive dairy cattle with 22 being group 2. One G. intestinalis positive human isolate was group 1 and four were group 2. Of the 724 faecal specimens examined two cows, 33 calves and 66 human specimens were positive for C. parvum. All 35 C. parvum positive dairy cattle exhibited the bovine genotype while the 66 positive humans showed a seasonal shift in the prevalent genotype with the bovine dominating the spring (100%) and the human dominating the late summer period (96%).

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