Benign bovine theileriosis (BBT) caused by Theileria sergenti / T. buffeli / T. orientalis complex is a tick borne disease occurs throughout the world (Radostitis et al 2007). Callow (1984) provides details on the disease in Australia. The parasite is widespread throughout Australia and in eastern Australia follows the distribution of Haemaphysalis longicornis and H. bancrofti. However despite the widespread distribution, losses due to T. buffeli were most unusual even though parasitaemias of up to 20% and occasionally higher occurred. This situation persisted till recently (Bock et al 2006). Since 2006, Industry and Investment NSW Veterinary Laboratories have received an increasing number of submissions where BBT was diagnosed. Recently Izzo et al (2010) reported on 8 cases of Theileria parasitaemias associated with marked anaemia. Of the properties, 5 were dairy and 3 were beef cattle enterprises. Disease occurred 6-12 weeks after introduction on 7 properties and on 1 property, homebred cattle were affected. Presenting complaints included inappetence and lethargy (8/8), mortality and stillbirths (6/8), abortion and poor milk production (3/8). The authors suggested an increase in clinical cases could be due to the increase in movement of cattle between dairy regions and/or the presence of a more virulent Theileria species. They also summarised previous attempts to clarify transmission of Theileria sp. by ticks. These studies showed that indigenous ticks H. bancrofti and H. humerosa were good vectors but that there was conflicting results as to whether H. longicornis transmitted infection. The questionnaire reported in this paper was conducted to obtain further information about BBT in NSW.
Selection of Properties
The Industry and Investment NSW Laboratory Information Management System was interrogated to identify submissions where testing for BBT theileriosis had occurred. This was supplemented by records of field veterinarians who submitted to other laboratories. A property diagnosis of BBT was made if: the PCV of one or more affected animals was <≡15 with evidence of regenerative anaemia or histological evidence of hypoxia; and smears made from blood (peripheral or capillary) had Theileria piroplasms; and babesiosis, anaplasmosis and other common causes of haemolytic anaemia were not suspected or had been excluded. Disease was diagnosed from September 2006-2010. Questionnaires were administered throughout 2010.
A questionnaire comprising of 76 questions was developed and piloted with 3 farmers prior to use. The questions could be divided into: general information about the property, animal health and management, specific mob based information and financial cost of disease. The questionnaire was administered by Livestock Health and Pest Authority (LHPA) veterinarians. Throughout the questionnaire respondents were asked questions about calves and adult cattle. Unless indicated otherwise, for the purposes of data analysis, steers and heifers (both unjoined and joined) were listed as adults.
Responses were received from 64 properties. Of these, 53 were beef and 11 were dairies.
Figure 1 provides details of locations. Forty four properties were located in coastal LHPAs with the Mid Coast containing the majority(32). Twenty properties were located in non coastal LHPAs. These were authorities with tableland and some slopes districts. While coastal LHPAs were defined as those which extended to the NSW coast, it resulted in inclusion of southern tablelands (Cooma and Bombala Council areas) and upper Hunter (Muswellbrook, Singleton and Upper Hunter Council areas) in the South East and Mid Coast LHPAs respectively. Similarly, it included farms in the eastern foothills of the Great Dividing Range (eg Walcha Council in the south eastern portion of New England LHPA) in non coastal LHPAs. Dairy farmers were predominately located in coastal LHPAs (10/11) while beef enterprises were distributed throughout the LHPAs represented. LHPAs which at the time of selection had not recorded cases of BBT included North West, Riverina, Hume, Western and Far Western.
Given the suspected involvement of ticks as vectors, a series of questions were asked regarding ticks. These are summarised in Table 2.
|Ticks observed in the 2 years prior to disease diagnosis||Properties that observed ticks- relative numbers of ticks in the year of diagnosis compared to previous 2 years|
Forty of 64 respondents recorded having seen ticks on their cattle in the 2 years prior to disease being diagnosed. Table 2 further divides properties according to location. As Haemaphysalis longicornis is distributed along the entire coast and into the tablelands of NSW and Haemaphysalis bancrofti is distributed on the north coast of NSW, it is expected that farmers in coastal LHPAs would see ticks. However 8/44 (18%) of coastal farmers did not record having seen ticks in the 2 years before disease was diagnosed suggesting ticks are either uncommon or underreported. However in at least one farm, the owners regarded as observant by the District Veterinarian who have a small stud, are adamant that ticks were not present though note that march flies were seen on the cattle. While ticks were observed on some properties from non coastal LHPAs, as expected, a greater proportion did not report ticks (16/20-80%). On two non coastal properties not reporting ticks, paddocks with affected cattle were sampled by dragging a blanket through the paddock in late spring 2010 with no ticks detected (On one of these properties, spread from coastal cattle to home animals occurred across a common fence). Of the properties reporting having seen ticks, the majority (28/37-76%) observed the same number of ticks on cattle as they had seen the previous 2 years.
Animal Health and Management
Practices such as ear tagging and multiuse needles that could result in the spread of blood from animal to animal were common. Castration when performed was via a knife, knife or rings or rings in 20, 4 and 27 properties respectively. Twenty one (84%) of respondents using a knife reported disinfecting the knife between calves.
Mob based disease information
Based on the responses received, 3 general categories were identified.
Calves: Fourteen beef properties recorded seeing disease in calves at foot but not their mothers. Disease was first noted in 2005, 2006, 2007, 2008, 2009 and 2010 in 1,1, 6, 4,and 1 properties respectively. Disease was first observed between July and January. One respondent did not indicate the year disease first occurred. These properties were located in the Mid Coast (9), North Coast (3) and New England (2) LHPAs. Within LHPAs topography included coastal valleys and foothills of the tablelands (up to an altitude of 842 metres above sea level). One North Coast property (Property 2) which traded cattle extensively also reported disease in introduced adult cattle. Most calves were born on the property though some had been purchased largely in the local area with their mothers. Calves averaged 13 weeks of age when first noticed sick with the youngest 9 and oldest 26 weeks of age. Cattle older than 8 months of age were rarely affected with no deaths from BBT reported in age groups other than calves. In 11 responses where numbers were provided, 89/1046 (8.5%) calves were affected and 55/1046 (5.2%) died.
Introduced adult cattle: thirty seven respondents indicated that disease had occurred in mobs of introduced cattle. In 27 responses it was possible to determine the time from introduction to disease. On average disease was seen 38 days after introduction with a range of 7-74 days and 1st , 2nd and 3rd quartiles of 32, 42 and 45.7 days respectively. Disease was first noted in 2005, 2006, 2008, 2009 and 2010 in 4, 5, 10, 12 and 4 properties respectively. The year was not indicated from 1 property. There was no seasonality with detection occurring in 10 months of the year. These properties were located in the Mid Coast (23), North Coast (5), New England (3), Central North (2) South East (2), Tablelands (1) and Cumberland (1) LHPAs. As noted previously, one North Coast property (Property 2) which traded cattle extensively also reported disease in calves. In general terms, cattle were moved from tableland or slopes districts, particularly in the south of the state and Victoria to coastal LHPAs. With the exception of Properties 40 (single bull from Western Australia) and 41 (steers from multiple sources), introduced cattle were cows or heifers in late pregnancy or cows with calves at foot (7 properties). Seventeen responses detailed the number of pregnant animals. Overall, 136/738 (18%) of cows or heifers aborted. Compared to other classes of cattle, introduced joined heifers and cows had high mortality rates with 69/751 (9.8%) and 174/662 (2.65) respectively. On the properties where cows and calves were introduced, a total of 25/178 (25%) calves were affected and 20/178 (11.2%) of calves died. However the questionnaire did not distinguish between sickness and death due to theileriosis in calves or through lack of milk.
Home adult cattle: Fourteen (12 beef and 2 dairies) respondents indicated that disease had occurred in mobs of home adult cattle [defined as bred on property or long term resident (>≡2 years) on the property]. Disease was first noted in 2008, 2009 and 2010 in 5, 5 and 4 properties respectively. Disease was first diagnosed most frequently in autumn [March (3), April (1) and May (1)] and spring [September(2), October(2) and November(1)]. These properties were located in the Tablelands (4), New England (2), Central North (2), Central West (2), Lachlan (2), South East (1) and Cumberland (1) LHPAs. In attempting to identify a potential source of infection, introduction of cattle from districts regarded as a high risk for Theileria infections was determined. In 10/14 properties, introduction of generally coastal cattle (Mid Coast or Cumberland LHPA) had occurred. In 9 responses, the time from introduction of high risk cattle to detection of disease in home adult cattle was given with an average of 111 days and a range of 51-181 days.
Cost of Disease
Farmers gave an average cost of $19,783 with a range of $300-204,000. This represented an average cost of $78/head (sum of all cattle present at the time of first diagnosis) with a range of $2-531/head. These are significant costs to the affected farmers.
This presentation at the DVs conference will discuss pertinent aspects of the survey, including the cost of the disease, the three syndromes observed and mechanisms to spread.
The assistance of Keith Hart, Ian Lugton, Jeff Eppleston and Barbara Moloney with design of the questionnaire and piloting (KH and IL) is gratefully acknowledged. The considerable efforts of Senior and District Veterinarians who administered the questionnaire and farmers for answering the questions is very much appreciated- without this assistance, the questionnaire would not have been possible.