Insecticidal Fly Tag Pilot Project – East Kimberley

In northern Australia, cattle are susceptible to insect-borne diseases which significantly impact cattle health and productivity; these include viral diseases Bovine Ephemeral Fever (BEF) and Akabane.   Traditionally, insecticidal fly tags have been employed to manage fly infestations, and while there have been anecdotal reports of their effectiveness in reducing fly worry and burden, their impact on disease transmission remains poorly understood.

Given the heightened biosecurity concerns surrounding Lumpy Skin Disease (LSD) in neighbouring countries, the Australian beef industry has become more vigilant and proactive in its reaction and preparedness for a domestic outbreak. Responding to concerns raised by members of the northern beef industry, the Department of Primary Industries and Regional Development (DPIRD) was requested to conduct a trial to explore preventative measures.

As a result, a pilot Insecticidal Fly Tag Trial was initiated during the 2022/2023 monsoon season in East Kimberley. The primary objective was to investigate the influence of insecticidal fly tags on the spread and infection rates of insect-borne diseases, as well as their impact on fly burden, fly worry, and overall cattle well-being.

Trial design

In late November 2022, a total of three hundred Brahman-cross heifers and steers were inducted into the trial. These animals were divided into two groups: the control group and the fly-tagged group. Blood samples were collected from all 300 animals to screen for arboviruses, BEF, and Akabane. Additionally, cattle weight, body condition score, and assessments for fly worry and fly burden were recorded the crush side.

Slow-release ear tags containing synthetic pyrethroids (beta-Cyfluthrin and Piperonyl butoxide) were applied to both ears of the fly-tagged treatment group.

Following the initial data collection, both trial groups were returned to their respective paddocks for a period of 16 weeks before being brought back to the yards for final assessment. The study involved the collection of blood samples, evaluation of fly infestation levels (including fly burden and fly worry scores), and weight measurements at weeks 1 and 16. The results yielded valuable insights into the effectiveness of fly tags in improving cattle health, productivity, and the marketability of stock.

After the initial diagnostic testing, approximately one-third (30%) of the trial animals were eliminated from the study due to testing positive for previous BEF, akabane, or both infections.

Preliminary Findings

Fly burden and fly worry

Fly burden and fly worry were scored using a system ranging from 0 to 5, with fly burden representing the level of fly population on the animal and fly worry indicating the level of fly irritation on the hide. The findings indicated a notable decrease in both fly burden and fly worry in the treatment group compared to the control. Average scores for fly burden and fly worry decreased in the treatment group by -0.4 and -0.6 respectively, while they increased in the control group by +1.2 and +0.5 respectively (Table 1).

Table 1. Average scores for fly burden and fly worry in the control and treatment groups.  A 5-point scoring scale was utilised with 5 being the highest burden/worry and 1 being the lowest.

Live weight

The presence of fly tags had a significant impact on live weight. The group treated with fly tags exhibited a greater weight gain compared to the control group, achieving a significantly higher live weight increase of 61.4 kg, in contrast to the control group’s gain of 46.9 kg as seen in Table 2. This translates to an average increase of 14.5 kg over the course of the 16-week trial. The treatment group saw a 50.1% increase in their body weight from week 1, while the control group experienced a 35.1% increase.

Table 2. Average live weight recorded at weeks 1 and 16 across both trial herds.

Disease

Regarding disease incidence, there was no statistically significant difference between the treatment and control groups (p=0.955) (Table 3). Both groups had similar percentages of cattle with positive or toxic VNT/ELISA results, indicating no substantial effect of the fly tags’ active ingredient on disease infection.

Table 3. VNT/ELISA results in relation to trial groups.

 Conclusion

While the field trial assessing the efficacy of insecticidal fly tags has revealed no notable effect in decreasing endemic disease seroconversion, it has indicated that fly tags effectively mitigate fly burden and irritation while enhancing live weight gains in cattle. The results show fly tags can be used as a tool to reduce the impact flies have on the health and productivity gains of cattle particularly during the northern Australian monsoon season.

Further research with different active ingredients in fly tags is recommended to explore whether insecticidal fly tags could provide protection against insect-borne diseases for the cattle industry.

This project is funded by the Department of Primary Industries and Regional Development (DPIRD).