Can You Tell the Difference?

By Teresa L. Steckler, University of Illinois Extension

Bovine anaplasmosis is not a new disease in Illinois. Once considered to only be a southern Illinois issue, data shows that positive cows are found throughout the state. Dr. Buzz Iliff and I have had numerous conversations about the disease and its presence near Lexington. It’s a problem, but one that can be managed.

Anaplasmosis, caused by the rickettsial hemoparasite Anaplasma spp. (A. marginale in the U.S.), can be transmitted via several different methods, but it is not contagious. Blood transfer must take place from an infected animal to an animal susceptible to infection. The disease commonly occurs during warm months when arthropods are abundant. Ticks are the most important biological vector with the Dermocentor (American dog tick or Wood tick) species implicated in most cases in the US, while mechanical transmission can occur through fly bites (horse and stable flies), mosquitoes, and blood contaminated needles and surgical instruments1.

Infection with bovine anaplasmosis can be divided into four stages: incubation, developmental, convalescent, and carrier. The incubation stage is the time from which the organism is introduced into a susceptible animal until 1% of red blood cells (RBCs) become infected, and during this time no clinical signs will be seen2. The developmental stage and clinical onset of anaplasmosis is determined by the incubation period, which varies from 15 to 45 days. Clinical signs appear as RBC production drops and more erythrocytes are parasitized and destroyed resulting in anemia. Studies indicate that some animals show signs with only a 10% loss of RBCs, while others indicate a 65% loss before onset of clinical signs2.

As the anemia becomes more severe, the acutely infected animals lose condition rapidly. Jaundice, weight loss, dehydration, constipation with hard dry feces shaded green, dark yellow urine, and progressive respiratory signs may become evident. Moreover, aggressive behavior, abortion in pregnant animals, and death due to hypoxia may occur2. An animal that survives a bout with anaplasmosis requires a convalescent period of up to 3 months.

So why am I writing about bovine anaplasmosis? What if I tell you that there is another disease that can clinically present as anaplasmosis but 1) is not treated like anaplasmosis; 2) can cause more losses than anaplasmosis; and 3) globally is one of four major tickborne diseases in cattle of significant economic importance.

I have briefly mentioned the disease before in an article; however, now is time for everyone to become much more aware of the disease and the potential economic impact in US cattle. The key difference between anaplasmosis and the newer disease – theileriosis - is that anaplasmosis rarely occurs in cattle less than 2 years of age; however, theileriosis has been observed in calves and adults. The theileriosis of major concern in the US is caused by Theileria orientalis Ikeda genotype. Cattle in the US are naïve, thus they do not have any degree of innate immunity.

So what is Theileria orientalis? T. orientalis are obligate intracellular protozoan parasites that infect both red and white blood cells, and cause bovine infectious anemia (characterized by hemolytic anemia, icterus, general malaise, ill thrift, and sporadic abortions)3,4,5. Clinical signs of theileriosis are similar to anaplasmosis in beef cattle (includes anemia, jaundice, and weakness). Occurrence of theileriosis is limited to the geographic distribution of appropriate tick vectors – the ixodid ticks6. In some endemic areas, indigenous cattle have a degree of innate resistance. Mortality in endemic areas is relatively low, but naïve/introduced cattle are particularly vulnerable.

T. orientalis Ikeda can spread rapidly and cause significant losses in cattle via anemia, abortion, and failure to thrive when introduced to naïve cattle and if competent tick vectors are present. The anemia can be so severe that cattle can die. T. orientalis Ikeda was first identified in Australia in 20117, and in 3 years, 25% of cattle had been affected by outbreaks of the disease8,9. Estimated indirect costs from reduced meat and milk yields8,10 to the Australian beef industry from T. orientalis Ikeda is $19.6 million per year11. New Zealand also experienced a sudden emergence of T. orientalis Ikeda in 201212. Periparturient and lactating dairy cows and young calves exhibited the highest morbidity and mortality12. An analysis of one dairy affected by T. orientalis in New Zealand in 2014 estimated the loss at more than $400 per cow13.

In the US the native genotypes of T. orientalis are usually nonpathogenic. However, T. orientalis Ikeda is virulent and was first identified in 2017 in Virginia6,14. Sale barns in Virginia saw the prevalence of T. orientalis increase from 2 to 20 percent in just two years (Dr. Kevin Lahmers, personal communication). Subsequently, the Ikeda genotype has been identified in Virginia, West Virginia, Tennessee, North Carolina, Pennsylvania, Kentucky, and Kansas14. However, it is possible that theileriosis from T. orientalis Ikeda is in other states and has not been correctly identified and/or reported due to clinical symptoms presenting like anaplasmosis. Unfortunately, the antibiotic used to treat A. marginale does NOT work to treat T. orientalis, and currently there is no approved treatment for T. orientalis in the US.

As stated above, the ixodid tick is a vector for T. orientalis. In the US, research from 2017 has shown that T. orientalis is being transmitted through the Asian longhorned tick (ALT)15,16, an ixodid tick. The ALT is native to East and Central Asia and slowly spreading in the US. Although the earliest known specimens of ALT in the U.S. were (retroactively) found in West Virginia in 2010, this tick made headlines in 2017 when numerous specimens were found on a ewe in Mercer County, New Jersey. Currently the tick has been found in 19 states: Arkansas, Connecticut, Delaware, Georgia, Indiana, Kentucky, Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, and West Virginia. Of particular importance are the sites closest to Illinois: northwest Missouri, southern Indiana, south central Kentucky, central to southern Ohio, and central to eastern Tennessee17.

While the ALT has been identified as a vector for T. orientalis, it is by no means the only mode of transference. Just like anaplasmosis, mechanical vectors, including contaminated needles18, biting flies18, and lice19, have been implicated in spreading the T. orientalis parasite from one animal to another. However, unlike transmission through needles, biting flies, and lice, once an ALT bites a cow infected with T. orientalis, the disease begins to reproduce rapidly inside the tick.

Something else that makes the ALT unique among other ticks in the U.S. — females can reproduce without mating in a process known as parthenogenesis. This is the primary mode, if not the only mode, of reproduction in U.S. populations. Females can lay approximately 2,500 eggs over the course of a few weeks. Known hosts for this tick include domestic cats, dogs, cattle, goats, horses, and sheep. Wild hosts include white-tailed deer, coyotes, foxes, groundhogs, Virginia opossums and raccoons. This tick has been occasionally found attached to humans and birds.

There have been several reports of thousands (and quite possibly millions) of ALTs infesting pastures and livestock. The ewe from Mercer County, New Jersey that sounded the alarm, had an estimated 12,000 ticks. The ewe was euthanized due to exsanguination. I have been told of at least 2 cattle herds in the Carolinas that were so heavily infested with ALT that they were euthanized as well. The closest story of exceedingly large numbers of ALTs affecting livestock was in southern Ohio. In 2021 a bull and two heifers were literally covered in such large numbers of ticks (tens of thousands) that the animals were euthanized (Risa Pesapane, personal communication). Pesapane and colleagues conducted drags on the farm and collected almost 10,000 ticks within about 90 minutes. She speculated that there were more than 1 million of them in the roughly 25-acre pasture (Risa Pesapane, personal communication).

Unfortunately, it is only a matter of time before the tick is in Illinois and ultimately T. orientalis Ikeda. Once T. orientalis Ikeda is in Illinois, based on losses elsewhere, up to 25% of a herd could be lost to theileriosis either through abortion or death of the calves and adults. Subsequently, herd productivity of those survivors will be reduced due to recovery time.

Movement of livestock, e.g. backgrounders from the southeastern part of the US where ALT and theileriosis is already present, or even wildlife movement can carry the tick into Illinois. If bringing livestock in from out of state and especially a state where the tick has been identified, it is important to quarantine in a dry lot area and treat the cattle for ticks. The cattle should be inspected for ticks - ears, brisket, vulva, etc. before turn out. It is very important to be vigilant and any time you work your cattle, check them for ticks. If you have an unusual clumping of ticks, collect several in a sealable bag and place them in a refrigerator. Contact me and I will have them properly identified and tested.

Source: Teresa L. Steckler, Extension Specialist, Commercial Agriculture, 618-695-4917, tsteckle@illinois.edu

1. Sonenshine DE. 1991. Biology of Ticks, vols. 1 and 2., 1st ed. Oxford University Press, Inc., New York, pp. 159–188.

2. Gill RN. Anaplasmosis in Beef Cattle. Texas A&M Extension Service B-5098. https://oaktrust.library.tamu.edu/handle/1969.1/87722 Accessed January 31, 2024.

3. Gebrekidan H, et al. 2020. An appraisal of oriental theileriosis and the Theileria orientalis complex, with an emphasis on diagnosis and genetic characterization. Parasitol Res 119:11–22

4. Kamau J, et al. 2011. Emergence of new types of Theileria orientalis in Australian cattle and possible cause of theileriosis outbreaks. Parasit Vectors 4:22

5. Oakes VJ, et al. 2019. Theileria orientalis Ikeda genotype in cattle, Virginia, USA. Emerg Infect Dis 25:1653–1659

6. OIE. Manual of Diagnostic Tests and Vaccines for Terrestrial Animals 2019: Chapter 3.4.14: Theilieriosis2020 https://www.oie.int/fileadmin/Home/eng/Health_standards/ tahm/3.04.14_THEILIERIOSIS.pdf Accessed January 31, 2024.

7. Islam MK, Jabbar A, Campbell BE, Cantacessi C, Gasser RB. 2011. Bovine theileriosis—an emerging problem in south-eastern Australia? Infect Genet Evol.11(8):2095–7.

8. Perera PK, Gasser RB, Anderson GA, Jeffers M, Bell CM, Jabbar A. 2013. Epidemiological survey following oriental theileriosis outbreaks in Victoria, Australia, on selected cattle farms. Vet Parasitol. 197(3–4):509–21.

9. Perera PK, Gasser RB, Firestone SM, Anderson GA, Malmo J, Davis G, et al. 2014. Oriental theileriosis in dairy cows causes a significant milk production loss. Parasit Vectors. 7:73.

10. Lawrence KE, Lawrence BL, Hickson RE, Hewitt CA, Gedye KR, Fermin LM, et al. 2019. Associations between Theileria orientalis Ikeda type infection and the growth rates and haematocrit of suckled beef calves in the north island of New Zealand. N Z Vet J. 67(2):66–73.

11. J. Lane TJ, R. Shepherd, J. Webb-Ware, G. Fordyce. 2015. Priority list of endemic diseases for the red meat industries. In: B.AHE.0010, editor. North Sydney: Meat and Livestock Australia Ltd. p. 76–81.

12. Lawrence K, McFadden A, Gias E, Pulford DJ, Pomroy WE. 2016. Epidemiology of the epidemic of bovine anaemia associated with Theileria orientalis (Ikeda) between August 2012 and March 2014. N Z Vet J.64(1):38–47.

13. Stafford KC, Williams SC, and Molaei G. 2017. Integrated Pest Management in Controlling Ticks and Tick-associated diseases. J Integrated Pest Mgmt 8:1-7.

14. Lahmers K. Theileria orientalis Ikeda genotype in cattle. https://vitals.vetmed.vt.edu/content/dam/vitals_vetmed_vt_edu/documents/theilieria-summary.pdf. Accessed January 31, 2024.

15. Thompson A, White S, Shaw D et al. 2020. Theileria orientalis Ikeda in host-seeking Haemaphysalis longicornis in Virginia, U.S.A. 11(5):101450.

16. Dinkel KD, Herndon DR, Noh SM, Lahmers KK, Todd SM, Ueti MW, Scoles GA, Mason KL, Fry LM. 2021. A U.S. isolate of Theileria orientalis, Ikeda genotype, is transmitted to cattle by the invasive Asian longhorned tick, Haemaphysalis longicornis. Parasit. Vectors 14:157.

17. https://www.cdc.gov/ticks/longhorned-tick/index.html. Accessed January 31, 2024.

18. Hammer JF, Jenkins C, Bogema D, Emery D. 2016. Mechanical transfer of Theileria orientalis: possible roles of biting arthropods, colostrum and husbandry practices in disease transmission. Parasit Vectors. 9:34.

19. Fujisaki K, Kamio T, Kawazu S, Shimizu S, Simura K. 1993. Theileria sergenti: experimental transmission by the long-nosed cattle louse, Linognathus vituli. Ann Trop Med Parasitol. 87(2):217–8.