Evidence that nitric acid increases relative humidity in low-temperature cirrus clouds

In situ measurements of the relative humidity with respect to ice (RHi) and of nitric acid (HNO3) were made in both natural and contrail cirrus clouds in the upper troposphere. At temperatures lower than 202 kelvin, RHi values show a sharp increase to average values of over 130% in both cloud types. These enhanced RHi values are attributed to the presence of a new class of HNO3-containing ice particles (Delta-ice). We propose that surface HNO3 molecules prevent the ice/vapor system from reaching equilibrium by a mechanism similar to that of freezing point depression by antifreeze proteins. Delta-ice represents a new link between global climate and natural and anthropogenic nitrogen oxide emissions. Including Delta-ice in climate models will alter simulated cirrus properties and the distribution of upper tropospheric water vapor.     

Prevalence and intensity of non-strongyle intestinal parasites of horses in northern Queensland

A quantitative post-mortem study of 57 horses from northern Queensland was done to determine the prevalence and intensity of non-strongyle intestinal parasites. The following species (% prevalence) were found: Draschia megastoma (39%); Habronema muscae (43%); Gasterophilus intestinalis (34%), G. nasalis (30%); Parascaris equorum (15%); Strongyloides westeri (6%); Probstmayria vivipara (2%); Oxyuris equi (26%); Anoplocephala magna (2%); A. perfoliata (32%). Mean parasite numbers of individual species ranged from 10 to 1310. Prevalence and intensity data were compared to recent studies in Western Australia and in the United States of America. Differences between stabled and paddocked horses were noted, particularly for botfly larvae and spiruroids. Climatic and seasonal changes in prevalence were restricted to H. muscae, G. nasalis and P. equorum with highest prevalence in the wet season or in horses from wet coastal areas. Only P. equorum showed any age effect being restricted to horses less than 5 years old. Breed and sex of horses was not important. The likelihood of changing parasite population dynamics with improved anthelmintic regimen is discussed.     

Comparison of the Q-fever complement fixation test and two commercial enzyme-linked immunosorbent assays for the detection of serum antibodies against Coxiella burnetii (Q-fever) in ruminants: Recommendations for use of serological tests on imported animals in New Zealand

Abstract

AIM: To make valid recommendations on the use of serological test methods for the detection of serum antibodies in ruminants against Coxiella burnetii (Q-fever), by comparing the performance of the complement fixation test (CFT) and two ELISA, and by identifying reasons for discrepancies between the test methods.

METHODS: A total of 73 serum samples from infected cattle, 69 from infected goats, and 100 samples from non-infected cattle and 57 samples from non-infected sheep, as well as 95 samples from infected cattle herds (mix of seropositive and seronegative samples), were tested using the CFT, the IDEXX ELISA (I-ELISA) and the Pourquier ELISA (P-ELISA). A mixed panel of 12 serum samples from sheep from inter-laboratory proficiency testing (proficiency panel) was also tested using the CFT and both ELISA, and further investigated using IgG- and IgM-specific ELISA.

RESULTS: Generally, the two commercial ELISA were more sensitive than the CFT for the detection of infected ruminants. Good agreement between ELISA for positive and negative results was found for samples from the infected herd, while results for the positive panels varied between the two ELISA. For the total of the positive serum panels, the I-ELISA detected 95% of samples as positive or suspicious, while the P-ELISA detected only 81%. In the P-ELISA, more samples were considered suspicious (18%) than in the I-ELISA (14%). All sera from noninfected sheep and cattle tested negative in the serological test methods employed, except for one positive sample from a sheep in the P-ELISA. Further investigation revealed that a CFT-positive but ELISA-negative result was due to high IgM and low IgG reactivity.

CONCLUSIONS: The two commercial ELISA were more sensitive than the CFT in all panels from infected ruminants. However, they could only detect IgG. The I-ELISA should be the serological test method of choice for cattle, sheep and goats for import testing of animals into New Zealand because it was more sensitive than the P-ELISA and was equally specific to the PELISA and the CFT. For other animal species, such as deer and camelids, the CFT should still be used since none of the ELISA has been evaluated for these species. This study has shown that the two commercial ELISA will detect the majority of infected ruminants but may miss animals that have not developed an IgG response.     

Strategic use of crutching and dicyclanil to protect unmulesed sheep against breech strike

Objective   To test strategies for the application of dicyclanil and mid-season crutching to maximise protection of unmulesed sheep against breech strike.
Procedure   Three hundred and eighty unmulesed Merino weaners were randomly allocated to four groups either left untreated or treated by different strategies with 50 g/L dicyclanil. Treatments included breech treatment alone and breech plus body treatment, with two application times, immediately after shearing and 6 weeks after crutching or shearing. To assess protection, larval implants with newly hatched Lucilia cuprina larvae were applied to 10 different sheep from each group at 3, 4, 5 and 6 months after crutching and shearing and assessed for the development of strike at 48 hours. The concentration of dicyclanil was measured in wool samples clipped from the breeches of the test sheep.
Results   All dicyclanil treatments gave significant reduction in strike in comparison to controls up until 4 months after crutching but protection in the sheep treated immediately after shearing had waned at 5 months. Treating at 6 weeks after crutching provided significant reduction ( P < 0.05) in strike for 6 months. Results for strike incidence immediately after shearing and concentration of dicyclanil in the breech wool also suggested improvements in protection by delaying treatment for 6 weeks.
Conclusion   In most environments it should be possible to protect unmulesed sheep against breech strike with a carefully planned integrated control program incorporating strategically timed crutching, shearing and dicyclanil application. Delaying treatment with dicyclanil to at least 6 weeks after shearing or crutching increased the protection provided in comparison to treatment immediately after shearing.