Additional disinfectants effective against the amphibian chytrid fungus Batrachochytrium dendrobatidis

Chytridiomycosis, a disease contributing to amphibian declines worldwide, is caused by the fungus Batrachochytrium dendrobatidis. Identifying efficient and practical disinfectants effective against B. dendrobatidis is important to reduce the spread of the disease both in the wild and captivity. Previous studies identified a range of suitable disinfectant strategies. We evaluated the suitability of 3 additional disinfectants: two of these (TriGene Virucidal Disinfectant Cleaner and F10 Super Concentrate Disinfectant) are mixtures of chemicals and one (Betadine Antiseptic Liquid) contains a single active ingredient, povidone iodine. The disinfectants were tested using a range of concentrations for 1,5 and 10 min to determine their ability to kill B. dendrobatidis in vitro. The measure of effectiveness was 100% kill of zoosporangia grown in multiwell plates. All disinfectants had a 100% efficacy at concentrations recommended by the manufacturers. The lowest concentrations capable of 100% kill after exposure for 1 min were 0.1 ml l(-1) for TriGene, 0.33 ml l(-1) for F10 and 100 ml l(-1) for Betadine. TriGene is the most effective disinfectant yet to be found, and both TriGene and F10 are more effective than various disinfectants tested in previous studies. TriGene and F10 are considered suitable for use in the field, as only small amounts of concentrate are needed.

The argument for integrating vector control with multiple drug administration campaigns to ensure elimination of lymphatic filariasis

BACKGROUND

There is a danger that mass drug administration campaigns may fail to maintain adequate treatment coverage to achieve lymphatic filariasis elimination. Hence, additional measures to suppress transmission might be needed to ensure the success of the Global Program for the Elimination of Lymphatic Filariasis.

DISCUSSION

Vector control successfully eliminated lymphatic filariasis when implemented alone or with mass drug administration. Challenges to lymphatic filariasis elimination include uncertainty of the exact level and duration of microfilarial suppression required for elimination, the mobility of infected individuals, consistent non-participation of some infected individuals with mass drug administration, the possible development of anti-filarial drug resistance and treatment strategies in areas co-endemic with loasis. Integration of vector control with mass drug administration can address some of these challenges. The potential benefits of vector control would include: (1) the ability to suppress filariasis transmission without the need to identify all individual 'foci of infection'; (2) minimizing the risk of reestablishment of transmission from imported microfilaria positive individuals; and (3) decreasing the risk of dengue or malaria transmission where, respectively, Aedes or Anopheles are lymphatic filariasis vectors.

SUMMARY

With adequate sustained treatment coverage, mass drug administration should meet the criteria for elimination of lymphatic filariasis. However, it may be difficult to sustain sufficiently high mass drug administration coverage to achieve lymphatic filariasis elimination in some areas, particularly, where Aedes species are the vectors. Since vector control was effective in controlling and even eliminating lymphatic filariasis transmission, integration of vector control with mass drug administration will ensure the sustainability of transmission suppression and thereby better ensure the success of national filariasis elimination programs. Although trials of some vector control interventions are needed, proven vector control strategies are ready for immediate integration with mass drug administration for many important vectors. Vector control is the only presently available additional lymphatic filariasis control measure with the potential for immediate implementation.

Freeman A, Speare R. Decline in the prevalence of chytridiomycosis in frog populations in North Queensland, Australia

In the early 1990s stream-associated amphibian populations in tropical upland North Queensland experienced severe declines resulting in extinction of three species, local elimination of four species, marked reductions in one species and apparently no declines in other species, Chytridiomycosis, a disease due to the amphibian chytrid fungus, Batrachochylrium dendrobatidis, was the likely cause of this epidemic. We conducted a monitoring study for chytridiomycosis in four species of frogs in North Queensland from October 1998 to October 2002 by collecting specimens in the field and using histology of removed digits to diagnose chytridiomycosis. Chytridiomycosis was diagnosed in 112 (7,1%) of the 1 578 specimens and prevalence was significantly associated with season and altitude, with higher prevalences in winter and above 300 metres altitude. A multivariate model adjusting for potential confounding effects arising from the sampling process demonstrated a significant decline in the time trend of prevalence of chytridiomycosis. The study supports the hypothesis that B. dendrobatidis becomes endemic after the initial epidemic wave. Since the surviving species of stream-associated frog, Litoria genimaculata, has increased to pre-decline numbers, the decline in prevalence of chytridiomycosis is evidence of a changed pathogen-host relationship. The reasons for this change are speculative but could be due to an increase in innate host resistance in response to selection pressure by B. dendrobatidis or to lower rainfall associated with an EI Nino effect. These findings justify management strategies that assist susceptible amphibian species to survive an initial epidemic wave of chytridiomycosis.

Head lice prevalence in primary schools in Victoria, Australia

OBJECTIVES

To determine the prevalence of and assess risk factors associated with head lice infections (pediculosis) in children from government primary schools in Victoria, Australia.

METHODS

Between May and October 2001, children were selected by clustered random sampling of schools and classes, then examined for head lice using hair conditioner and a fine-toothed head lice comb. There were 1838 children screened from 16 primary schools. Risk factors evaluated included metropolitan or rural residence, school class, gender and hair length.

RESULTS

Thirteen percent of children (239/1838) had an active infection (95% CI, 10.9-15.1) and 3.3% (61/1838) had an inactive infection (95% CI, 2.0-4.6). Prevalence of active pediculosis varied between schools from 0 to 28%. Our screening identified no more than one case per class in the majority of classes screened (58.5%). Females were 2.2 times more likely to have active infection than males (95% CI [1.7,2.9]) and there was no significant difference for the other risk factors investigated.

CONCLUSIONS

Our study demonstrated the prevalence of head lice varied across Victoria and showed that risk factors commonly attributed to head lice infections did not hold true. Our findings support the premise that traditional ad hoc mass school-based screening may not be the best use of resources when controlling head lice. We suggest a more pragmatic community-based approach.

Adaptive immunity in melioidosis: a possible role for T cells in determining outcome of infection with Burkholderia pseudomallei

Melioidosis is a potentially fatal disease caused by the bacterium Burkholderia pseudomallei. Individuals with subclinical melioidosis have no apparent clinical signs or symptoms, and are identified only by positive serology. The present study is the first to investigate cell-mediated immune (CMI) responses following in vitro stimulation with B. pseudomallei antigens in peripheral blood mononuclear cells (PBMC), collected under field conditions in Papua New Guinea (PNG) from individuals with exposure to B. pseudomallei (n = 13). While five had a clinical history of melioidosis (C(+)), the remaining individuals (n = 8) were seropositive, yet healthy with no clinical history of melioidosis (S(+)/C(-)). Proliferation and IFN-gamma production were significantly greater in lymphocyte cultures from S(+)/C(-) individuals compared to C(+) individuals (P < 0.001 and P < 0.05, respectively). These findings demonstrate that compared to C(+) patients, individuals with subclinical melioidosis have a stronger CMI response to B. pseudomallei antigens in vitro. Such a response may be essential for protection against disease progression.

Strongyloides serology--useful for diagnosis and management of strongyloidiasis in rural Indigenous populations, but important gaps in knowledge remain

General practitioners who care for Aboriginal patients in rural and remote communities from tropical Australia must be aware of strongyloidiasis. The prevalence of this parasitic infection is high and occasional cases can have a fatal outcome. Other groups in Australia at high risk of strongyloidiasis are immigrants from endemic countries, particularly from Southeast Asia, and military personnel who have served overseas in endemic areas. Elimination programs for enteric parasites in rural Australian Indigenous communities are so important that a nationally coordinated approach has been advocated. Wisely used, cost-effective diagnostic tests are a critical component of an elimination program. Strongyloidiasis must be confirmed by laboratory diagnosis and the strongyloides ELISA, although not ideal, is a useful test that can be used to diagnose strongyloidiasis and to monitor cure. In this article the value of the current strongyloides ELISA is discussed and a cost-benefit analysis is conducted using direct costs only. In a typical rural Aboriginal community in tropical Australia with prevalence of strongyloidiasis at 20% each true positive case detected by the strongyloides ELISA is estimated to cost approximately AU590 dollars to diagnose and manage until cure, proven by negative serology.

Effect of season and temperature on mortality in amphibians due to chytridiomycosis

OBJECTIVE

To investigate the distribution and incidence of chytridiomycosis in eastern Australian frogs and to examine the effects of temperature on this disease.

DESIGN

A pathological survey and a transmission experiment were conducted.

PROCEDURE

Diagnostic pathology examinations were performed on free-living and captive, ill and dead amphibians collected opportunistically from eastern Australia between October 1993 and December 2000. We conducted a transmission experiment in the laboratory to investigate the effects of temperature: eight great barred frogs (Mixophyes fasciolatus) exposed to zoospores of Batrachochytrium dendrobatidis and six unexposed frogs were housed individually in each of three rooms held at 17 degrees C, 23 degrees C and 27 degrees C.

RESULTS

Chytridiomycosis was the cause of death or morbidity for 133 (55.2%) of 241 free-living amphibians and for 66 (58.4%) of 113 captive amphibians. This disease occurred in 34 amphibian species, was widespread around the eastern seaboard of Australia and affected amphibians in a variety of habitats at high and low altitudes on or between the Great Dividing Range and the coast. The incidence of chytridiomycosis was higher in winter, with 53% of wild frogs from Queensland and New South Wales dying in July and August. Other diseases were much less common and were detected mostly in spring and summer. In experimental infections, lower temperatures enhanced the pathogenicity of B. dendrobatidis in M. fasciolatus. All 16 frogs exposed to B. dendrobatidis at 17 degrees C and 23 degrees C died, whereas 4 of 8 frogs exposed at 27 degrees C survived. However, the time until death for the frogs that died at 27 degrees C was shorter than at the lower temperatures. Infections in survivors were eliminated by 98 days.

CONCLUSION

Chytridiomycosis is a major cause of mortality in free-living and captive amphibians in Australia and mortality rate increases at lower temperatures.

A squamous cell carcinoma and an adenocarcinoma in Australian treefrogs

We describe the pathology in a captive adult White lipped treefrog (Litoria infrafrenata) with a squamous cell carcinoma of the skin and a free-living adult Common green treefrog (L. caerulea) with an adenocarcinoma of the skin. Although many amphibian neoplasms have been reported world wide, none had been described in Australian species.

Strongyloidiasis: an issue in Aboriginal communities

Strongyloidiasis, a disease caused by the parasitic gut nematode (roundworm), Strongyloides stercoralis, has the highest prevalence in the world in rural and remote Aboriginal communities of northern Australia. With prevalences greater than 25%, these communities have rates of strongyloidiasis higher those in the worst affected developing countries where surveys have been recently conducted. Available data indisputably support that strongyloidiasis is more prevalent in rural and remote Aboriginal communities than in the mainstream Australian community. However control of strongyloidiasis has not been given a high priority by government health departments, with the result that Aboriginal people in remote and rural communities in Northern Australia are still suffering from a preventable and treatable disease. This article suggests that the only way to address the strongyloidiasis problem in Indigenous communities is to have strongyloidiasis recognised and addressed at the national level. One component of this must be making health departments responsible for establishing appropriate systems of effective treatment for and monitoring of patients with strongyloidiasis.

Leprosy in Mpumalanga Province, South Africa--eliminated or hidden?

In South Africa, leprosy has been a notifiable condition since 1921. Although the WHO elimination target of less than one case per 10,000 population has been achieved at country level, the distribution of leprosy in the country is distinctly heterogeneous, with a prominent 'leprosy belt' of greater prevalence stretching across Mpumalanga Province into northern Kwa-Zulu Natal. The highest prevalence in this 'belt' has historically been in Ermelo District. Recent trends of few newly detected leprosy patients in this district raised concerns that health system changes may have resulted in failure to detect leprosy cases. Thus a large-scale community awareness campaign was conducted followed by an intensively advertised screening programme of 3-month duration at schools and central gathering points in villages and farms from 1 June to 31 August 2000. One thousand one hundred and seventy-seven people presented for clinical screening at designated points, while 790 scholars were screened at schools and an additional 1433 people were screened at their homes by the field team. Forty-four people with skin or nervous system lesions compatible with leprosy were referred for specialized assessment and biopsy where indicated. Four new leprosy patients were diagnosed, including an elderly lady with pronounced disability. Two of these patients had prior contact with the health service due to dermatological manifestations of leprosy without diagnosis being made. All patients provided a history of close prolonged contact with known leprosy patients. Ongoing intense tracing and follow-up of close contacts of proven leprosy cases may be a more efficient method of detecting leprosy cases in areas with relatively stable populations that have accomplished 'leprosy elimination', than resource intensive community surveys.

Rabies post-exposure management in South Africa: a telephonic survey used as a rapid tool for operational research

Rabies is an important disease in rural South Africa, and vaccine and immunoglobulin are provided, at the State's expense, to humans following suspected exposure to rabies virus by bite, scratch or mucosal splash. Health facilities where post-exposure treatment is available are listed, with contact telephone numbers, in national rabies guidelines. To verify the accuracy of this recently updated information, members of the national Rabies Advisory Group were tasked to complete a rapid survey. A simple standardized telephone interview technique was used. This revealed startling deficiencies in the availability of vaccine and immunoglobulin at the indicated sites and led to decisive corrective action. This 'quick and dirty' survey technique provided valuable information for improving an important public health programme, and should be considered when auditing other health programmes, particularly where a means for validating responses is readily available.

A case of pubic lice resistant to pyrethrins

BACKGROUND

Effective therapeutic protocols for the treatment of pubic lice include application of approved insecticidal products to all body and scalp hair, retreatment at seven days, and use of mechanical removal of lice and eggs.

OBJECTIVE

We report here infection with pubic lice in a 43 year old male in Australia which failed to be eradicated by adequate therapy with a pyrethrin and piperonyl butoxide product.

DISCUSSION

Pubic lice collected from the case survived after exposure to the same product in vitro. The infestation was cured by use of 5% permethrin. This appears to be the first report of Pthirus pubis resistant to insecticides, in this case pyrethrins and their synergist, piperonyl butoxide.

Salmonelliasis in wildlife from Queensland

During a 20 yr period (1978 to 1998), 233 isolates of Salmonella spp. were cultured from 179 wildlife animals (representing 25 species), 32 crocodile (Crocodylus porosus) eggs and six crocodile nesting sites, and represented 59 different serotypes. Salmonella serotype Virchow, the major serotype infecting humans in north Queensland, (Australia) was common in macropodids, but was not found in reptiles and was isolated only once from cane toads (Bufo marinus). Investigations of human cases of salmonellosis should include simultaneous studies on wild and domestic animals in contact with the case.

The use of hospital-based nurses for the surveillance of potential disease outbreaks

OBJECTIVE

To study a novel surveillance system introduced in Mpumalanga Province, a rural area in the north-east of South Africa, in an attempt to address deficiencies in the system of notification for infectious conditions that have the potential for causing outbreaks.

METHODS

Hospital-based infection control nurses in all of Mpumalanga's 32 public and private hospitals were trained to recognize, report, and respond to nine clinical syndromes that require immediate action. Sustainability of the system was assured through a schedule of regular training and networking, and by providing feedback to the nurses. The system was evaluated by formal review of hospital records, evidence of the effective containment of a cholera outbreak, and assessment of the speed and appropriateness of responses to other syndromes.

FINDINGS

Rapid detection, reporting and response to six imported cholera cases resulted in effective containment, with only 19 proven secondary cholera cases, during the two-year review period. No secondary cases followed detection and prompt response to 14 patients with meningococcal disease. By the end of the first year of implementation, all facilities were providing weekly zero-reports on the nine syndromes before the designated time. Formal hospital record review for cases of acute flaccid paralysis endorsed the value of the system.

CONCLUSION

The primary goal of an outbreak surveillance system is to ensure timely recognition of syndromes requiring an immediate response. Infection control nurses in Mpumalanga hospitals have excelled in timely weekly zero-reporting, participation at monthly training and feedback sessions, detection of priority clinical syndromes, and prompt appropriate response. This review provides support for the role of hospital-based nurses as valuable sentinel surveillance agents providing timely data for action.

Prevalence of filarial antigenaemia in Papua Nnew Guinea: results of surveys by the School of Public Health and Tropical Medicine, James Cook University, Townsville, Australia

During the period from 1991 to 1997 the School of Public Health and Tropical Medicine, James Cook University carried out filariasis surveys in several parts of Papua New Guinea using the newly introduced Onchocerca gibsoni monoclonal (Og4C3) and immunochromatographic test (ICT) antibody-based assays for filarial antigen and, in some cases, a Knott's test for microfilariae. The average prevalence of filarial antigenaemia and microfilaraemia was 56% and 35% respectively confirming earlier survey results that filariasis is hyperendemic in many parts of the country. The antigen tests detected 25% more cases than the Knott's test and the simplicity of the ICT and its capacity to produce almost instant results make it an ideal tool for surveys.