Infectivity and persistence of an outbreak strain of Salmonella enterica serotype Typhimurium DT160 for house sparrows (Passer domesticus) in New Zealand

AIM: To examine the infective dose, incubation period and disease progression of an isolate of Salmonella enterica serotype Typhimurium definitive type 160 (DT160) originating from a naturally-infected house sparrow (Passer domesticus) during an outbreak of the disease in New Zealand.

METHODS: Thirty-six house sparrows captured from the wild and free of Salmonella spp were divided into six groups of six birds, housed individually, and inoculated orally with phosphate buffered saline (PBS) or 10¹, 10², 10³, 10⁵, 2 × 10⁸ colony forming units (cfu) of the outbreak strain of S. Typhimurium DT160. The birds were observed for 10 days for clinical signs and/or mortality, and faecal samples were collected to determine excretion of S. Typhimurium. The birds were eutha- nised 11 days post-inoculation (p.i.) and a wide range of tissue samples were collected for histopathological examination, and culture and typing of Salmonella spp. Macro-restriction profiling by pulsed-field gel electrophoresis (PFGE) using XbaI was performed for the epidemiological typing of S. Typhimurium DT160 isolates.

RESULTS: Mortality in house sparrows inoculated with S. Typhimurium DT160 was dose-dependent, and 2/6 birds inoculated with ¹⁰⁵ cfu and all six birds inoculated with 2 × 10⁸ cfu died during the study. Infected sparrows displayed few clinical signs, apart from diarrhoea and/or polyuria, fluffed plumage, and sitting on the floor of the cage. Faecal excretion of DT160 occurred briefly in two birds inoculated with 10² cfu and four birds inoculated with 10³ cfu, on most days in five birds inoculated with 10⁵ cfu, and continuously in six birds inoculated with 2 × 10⁸ cfu. DT160 was isolated from the livers of three birds which received 10³ cfu, five birds dosed with 10⁵ cfu, and all six birds given 2 × 10⁸ cfu. Following necropsy, histopathological lesions similar to those seen in the natural disease were observed in the liver or spleen of three birds which received 10³ cfu, and all birds dosed with ≥10⁵ cfu.

CONCLUSION: The results indicate that an isolate of S. Typhimurium DT60 originating from house sparrows in New Zealand is pathogenic to these birds and that the response is dose- dependent. The persistence and excretion of the pathogen may last for at least 10 days. This confirms that sparrows infected with DT160 could be a source of infection to humans and other in-contact animals.     

Magnetic microstructure of magnetotactic bacteria by electron holography

Off-axis electron holography in the transmission electron microscope was used to correlate the physical and magnetic microstructure of magnetite nanocrystals in magnetotactic bacteria. The magnetite crystals were all single magnetic domains, and the magnetization directions of small superparamagnetic crystals were constrained by magnetic interactions with larger crystals in the chains. Shape anisotropy was found to dominate magnetocrystalline anisotropy in elongated crystals. A coercive field between 300 and 450 oersted was determined for one chain.     

Crypt abscesses in the caeca of feral rabbits in a rabbit haemorrhagic disease endemic region of New Zealand

AIM: To describe the pathology of crypt abscesses in the caeca of feral rabbits in the Manawatu region of New Zealand, and to examine the possible relationship between their prevalence and rabbit haemorrhagic disease (RHD) virus (RHDV) infection.

METHODS: During the course of a 3-year study of RHD, 173 wild rabbits (Oryctolagus cuniculus) were shot on three pastoral livestock farms in the Manawatu region of New Zealand. All rabbits were necropsied, and tissue samples of the caeca were examined histologically. The age of each animal was determined, and blood samples collected for the detection of RHDV antibodies. Logistic regression was used to model the odds of rabbits having crypt abscesses.

RESULTS: At necropsy, 63/173 (36.4%) rabbits were found to have small circular black nodules on the mucosal surface of their appendix caecum and/or sacculus rotundus. Microscopically, these were identified as small crypt abscesses composed of dilated sacs at the base of the mucosa that were often lined by a thin layer of attenuated epithelial cells. They usually contained large amounts of concentrically-laminated mucopolysaccharide material that was sometimes pigmented, inflammatory debris, and were often the site of a moderate multifocal appendicitis. Although RHDV was active in the study area, no association was found between RHDV antibodies in serum and the presence of lesions. The lesions were more common in older individuals and those born in summer or autumn.

CONCLUSIONS: This is the first report of crypt abscesses with inflammation and necrotic debris in the caeca of rabbits. No association between the occurrence of crypt abscesses and RHDV infection was identified. Wild rabbits born in a particular season were presumably exposed very early in life to conditions that caused the crypt abscesses to develop. Alternatively, association with season of birth may represent rabbits that were of similar age in a later stage of their lives, when they became exposed to the cause of the lesions, which remains unidentified.     

Mayan urbanism: impact on a tropical karst environment

From the first millennium B.C. through the 9th-century A.D. Classic Maya collapse, nonurban populations grew exponentially, doubling every 408 years, in the twin-lake (Yaxha-Sacnab) basin that contained the Classic urban center of Yaxha. Pollen data show that forests were essentially cleared by Early Classic time. Sharply accelerated slopewash and colluviation, amplified in the Yaxha subbasin by urban construction, transferred nutrients plus calcareous, silty clay to both lakes. Except for the urban silt, colluvium appearing as lake sediments has a mean total phosphorus concentration close to that of basin soils. From this fact, from abundance and distribution of soil phosphorus, and from continuing post-Maya influxes (80 to 86 milligrams of phosphorus per square meter each year), which have no other apparent source, we conclude that riparian soils are anthrosols and that the mechanism of long-term phosphorus loading in lakes is mass transport of soil. Per capita deliveries of phosphorus match physiological outputs, approximately 0.5 kilogram of phosphorus per capita per year. Smaller apparent deliveries reflect the nonphosphatic composition of urban silt; larger societal outputs, expressing excess phosphorus from deforestation and from food waste and mortuary disposal, are probable but cannot be evaluated from our data. Eutrophication is not demonstrable and was probably impeded, even in less-impacted lakes, by suspended Maya silt. Environmental strain, the product of accelerating agroengineering demand and sequestering of nutrients in colluvium, developed too slowly to act as a servomechanism, damping population growth, at least until Late Classic time.     

Oestrous sheep serum balances ROS levels to supply in vitro capacitation of ram spermatozoa

Reactive oxygen species (ROS) are fundamental for intracellular signalling. In spermatozoa, they are involved both to apoptosis and to capacitation, and changes in ROS levels can alter the balance between these two processes. Oestrous sheep serum (OSS) is considered an efficient agent for in vitro capacitation of ram spermatozoa. We have explored the effects of OSS on ram sperm physiology, especially on ROS production, during in vitro capacitation. Semen samples from 15 rams were cryopreserved. After thawing, samples were submitted to four treatments: control (CTL), 10% OSS supplementation for in vitro sperm capacitation, caspase inhibitor (INH, Z‐VAD‐FMK 100 μM) and OSS (10%) plus caspase inhibitor (I + E). Sperm samples were incubated for 30 min at 38.5°C and 5% CO₂ and evaluated motility and kinetic parameters by computer‐assisted semen analysis (CASA) and viability (propidium iodide), apoptotic‐like membrane changes (YO‐PRO‐1), acrosomal status (PNA‐FITC), intracellular calcium (FLUO‐3), membrane fluidity (M540) and ROS production (CM‐H₂DCFDA) by flow cytometry. OSS induced changes in kinetic parameters compatible with capacitation, with a decrease in the percentage of progressive motility and linearity, and an increase in the amplitude of the lateral displacement of the sperm head (p < .05). Moreover, OSS increased the proportion of M540+ viable spermatozoa, YO‐PRO‐1+ and acrosome‐reacted spermatozoa (p < .05). After incubation, OSS and I+E achieved lower ROS levels (p < .05). Ca²⁺ levels did not change with the incubation, but were slightly higher (p < .05) when both OSS and the inhibitor were present. We suggest that OSS may modulate ROS levels, allowing intracellular signalling for capacitation to occur while preventing higher levels that could trigger apoptosis.     

Antibiotics for the preservation of koala (Phascolarctos cinereus) semen

Aim To determine the normal microbial flora of the koala ejaculate and prepuce in order to select appropriate antibiotics for addition into diluents designed for the preservation of semen.
Procedure Bacteriological samples of the koala prepuce (n = 12) and ejaculate (n = 20) were submitted for microbial culture and sensitivity testing. Microbial flora of ejaculates collected by electroejaculation and artificial vagina were compared. The effects of varying concentrations of penicillin G and gentamicin on sperm motility and on the growth of bacteria in diluted semen stored at room temperature and 16°C over a 24 h period were investigated.
Results A range of bacteria was isolated from the koala prepuce and ejaculate. The predominant organisms in semen collected by electroejaculation and artificial vagina were Corynebacterium spp, none of which could be assigned to any recognised species. The addition of penicillin G and gentamicin to a PBS-based diluent at dose rates of 1000 to 2000 IU/mL and 100 to 200 m g/mL respectively, resulted in no adverse effect on sperm motility over a 24 h incubation period. Penicillin G (1000 IU/mL) and gentamicin (100 m g/mL) prevented growth of bacterial contaminants in diluted koala semen.
Conclusion By controlling the growth of bacteria in extended koala semen, penicillin G and gentamicin are likely to lengthen the period by which spermatozoa can be stored at 16°C and reduce the possibility of disease transmission during artificial insemination procedures.     

Twinning and embryonic mortality in a free-living kaka (Nestor meridionalis)

Abstract

Compared to mammals, twinning in birds is rare. The reported incidence in domestic chickens (Gallus gallus) is 0.11 % (Byerly and Olsen 1934 Byerly, TC and Olsen, MW. 1934. Polyembryology in the domestic fowl. Science, 80: 247–248.  [Google Scholar]) and in pigeons (Columba livia) only 0.07% (Riddle 1923 Riddle, O. 1923. The causes of twinning and abnormal development in birds. American Journal of Anatomy, 32: 199–252.  [Google Scholar]). Monozygotic twins occur following the fission of an early embryo and may or may not share the same yolk. Dizygotic twins are thought to occur following 2 simultaneous ovulations or perhaps by the slow passage of an ovum down the oviduct, resulting in it being caught by a succeeding yolk and then being incorporated into the same membrane and shell (Harrison 1986 Harrison, GJ. 1986. “Reproductive Medicine”. In Clinical Avian Medicine and Surgery, Edited by: Harrison, GJ and Harrison, LR. 620–633. Philadelphia: WB Saunders.  [Google Scholar]). Regardless of their origin most avian twins do not survive beyond hatching.     

Concurrent avian malaria and avipox virus infection in translocated South Island saddlebacks (Philesturnus carunculatus carunculatus)

Abstract

CASE HISTORY: Outbreaks of mortality in South Island saddlebacks (Philesturnus carunculatus carunculatus) that had been translocated to two offshore islands in the Marlborough Sounds of New Zealand were investigated during the summer of 2002 and 2007. Both outbreaks were associated with a severe decrease in numbers of saddlebacks of up to 60% of approximately 200 birds.

CLINICAL AND PATHOLOGICAL FINDINGS: Many of the surviving birds were in poor condition, and had skin lesions on the legs and head. Necropsy showed pale liver and lungs, and a swollen spleen. Histopathology revealed schizonts resembling Plasmodium spp. within the cytoplasm of many hepatocytes and splenic histiocytes. The skin lesions consisted of epithelial proliferations containing numerous Bollinger bodies typical of avipox virus (APV) infection. Two different APV were isolated, using PCR, from two different birds exhibiting skin lesions. Each isolate had 100% sequence homology with APV members from either Clade A or Clade B. In addition, PCR analysis revealed that the Plasmodium elongatum present in infected birdsbelonged to a strain that was endemic in the population of North Island saddlebacks (Philesturnus carunculatus rufusater).

DIAGNOSIS: Concurrent infections with Plasmodium spp. haemoparasites and APV were identified as the likely cause of death in the birds examined.

CONCLUSIONS AND CLINICAL RELEVANCE: Although the Plasmodium spp. identified is thought to be endemic to saddlebacks in New Zealand, the affected birds were likely to be immunocompromised by concurrent APV infection or through lack of genetic diversity. Both the introduced mosquito Culex quinquefasicatus and the native mosquito Culex pervigilans are likely vectors for both these diseases, and the provision of water supplies less favourable to mosquito-breeding is recommended.